fix(security): validate enrollment summary branding image URL (https-only, no quotes); launcher drops unsafe URLs instead of interpolating them into the dialog command line

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/backend/tenant-activation-welcome-mail.md

@@ -107,6 +107,13 @@ properties `Html`, `UpdatedBy`, `UpdatedUtc`), cached 5 minutes, invalidated on
 
 * The only placeholder is `{{domainName}}`; an empty domain renders as "your organization",
   matching the built-ins. Subjects are not editable (pinned constants).
+* The domain is HTML-encoded at the point of substitution (`EmailTemplateService.Render` and the
+  built-in template builders) — the mail goes out under the product's signed sender to a
+  tenant-chosen recipient, so no writer of `DomainName` may ever inject markup into it.
+  `DomainName` itself is tenant identity: seeded once at first login from the UPN domain
+  (`AuthFunction`, only when it passes `TenantConfigValidation.IsValidDomainName` — a strict
+  dotted host name), preserved from the stored row on the full-model config PUT for every
+  caller, and "never writable" in the field-patch flow.
 * Limit 30 000 characters (Table string property cap is 32K UTF-16 chars).
 * The send path is fail-soft: a storage error falls back to the built-in body. The admin
   read path is not — a broken store surfaces as an error instead of silently showing the

docs/log.md

@@ -1,5 +1,9 @@
 # Log
 
+## 2026-08-29 (10)
+
+* **Update**: `backend/tenant-activation-welcome-mail.md` — welcome/farewell mails HTML-encode the domain at substitution; `DomainName` is frozen on the full-model config PUT (was persisted verbatim) and the first-login seed only accepts a strict DNS host name.
+
 ## 2026-08-29 (9)
 
 * **Update**: `agent/decision-engine.md`, `agent/overview.md` — `SignalIngress.Post` is worker-thread re-entrancy-safe: signals the worker posts to itself from inside `ApplyStep` (EffectRunner `ClassifierVerdictIssued`) go to a worker-local follow-up queue drained ahead of the bounded channel instead of blocking on it, so a full channel can no longer deadlock the single consumer.

src/Agent/AutopilotMonitor.Agent.V2.Core.Tests/Termination/SummaryDialogLauncherTests.cs

@@ -50,5 +50,42 @@ namespace AutopilotMonitor.Agent.V2.Core.Tests.Termination
 
             Assert.Equal(a, b);
         }
+
+        // The branding URL is tenant config; the dialog parses arguments last-occurrence-wins, so
+        // an embedded quote must never terminate the argument and inject extra flags (CWE-88).
+
+        private const string BaseArgs = "--status-file \"C:\\x\\final-status.json\" --timeout 30 --cleanup";
+
+        [Fact]
+        public void BuildDialogArguments_omits_branding_when_empty()
+        {
+            var args = SummaryDialogLauncher.BuildDialogArguments(@"C:\x\final-status.json", 30, null, null);
+
+            Assert.Equal(BaseArgs, args);
+        }
+
+        [Fact]
+        public void BuildDialogArguments_appends_clean_https_url_as_single_quoted_argument()
+        {
+            var args = SummaryDialogLauncher.BuildDialogArguments(@"C:\x\final-status.json", 30, "https://cdn.example/logo.png?v=2", null);
+
+            Assert.Equal(BaseArgs + " --branding-url \"https://cdn.example/logo.png?v=2\"", args);
+        }
+
+        [Theory]
+        [InlineData("x\" --status-file \"C:\\some\\file\" --timeout \"0")]
+        [InlineData("https://cdn.example/logo.png\" --cleanup")]
+        [InlineData("https://cdn.example/logo.png --timeout 0")]
+        [InlineData("https://cdn.example/lo'go.png")]
+        [InlineData("https://cdn.example/logo.png\r\n")]
+        [InlineData("http://cdn.example/logo.png")]
+        [InlineData("file:///C:/Windows/x.png")]
+        [InlineData("cdn.example/logo.png")]
+        public void BuildDialogArguments_drops_unsafe_branding_url(string url)
+        {
+            var args = SummaryDialogLauncher.BuildDialogArguments(@"C:\x\final-status.json", 30, url, null);
+
+            Assert.Equal(BaseArgs, args);
+        }
     }
 }

src/Agent/AutopilotMonitor.Agent.V2.Core/Termination/SummaryDialogLauncher.cs

@@ -132,10 +132,11 @@ namespace AutopilotMonitor.Agent.V2.Core.Termination
             }
 
             // 4) Compose args. Legacy contract: --status-file <path> --timeout <s> --cleanup [--branding-url <url>].
-            var tempStatusArg = Path.Combine(tempDir, FinalStatusFileName);
-            var args = $"--status-file \"{tempStatusArg}\" --timeout {configuration.EnrollmentSummaryTimeoutSeconds} --cleanup";
-            if (!string.IsNullOrWhiteSpace(configuration.EnrollmentSummaryBrandingImageUrl))
-                args += $" --branding-url \"{configuration.EnrollmentSummaryBrandingImageUrl}\"";
+            var args = BuildDialogArguments(
+                Path.Combine(tempDir, FinalStatusFileName),
+                configuration.EnrollmentSummaryTimeoutSeconds,
+                configuration.EnrollmentSummaryBrandingImageUrl,
+                logger);
 
             // 5) Launch in user session with retry.
             var retrySeconds = configuration.EnrollmentSummaryLaunchRetrySeconds > 0
@@ -151,6 +152,44 @@ namespace AutopilotMonitor.Agent.V2.Core.Termination
             return launched;
         }
 
+        /// <summary>
+        /// Composes the dialog command line. The branding URL is tenant-supplied config and the
+        /// dialog parses arguments last-occurrence-wins, so a value carrying a double quote could
+        /// terminate its argument and override <c>--status-file</c>/<c>--timeout</c>/<c>--cleanup</c>
+        /// (CWE-88). The backend rejects such values, but the agent is the last line of defence:
+        /// only a plain absolute HTTPS URL without quotes, whitespace or control characters is
+        /// ever placed on the command line — anything else is dropped (the dialog then simply
+        /// shows no branding image).
+        /// </summary>
+        internal static string BuildDialogArguments(string statusFilePath, int timeoutSeconds, string brandingImageUrl, AgentLogger logger)
+        {
+            var args = $"--status-file \"{statusFilePath}\" --timeout {timeoutSeconds} --cleanup";
+            if (string.IsNullOrWhiteSpace(brandingImageUrl))
+                return args;
+
+            if (IsSafeBrandingImageUrl(brandingImageUrl))
+                return args + $" --branding-url \"{brandingImageUrl}\"";
+
+            logger?.Warning("SummaryDialogLauncher: EnrollmentSummaryBrandingImageUrl is not a plain absolute HTTPS URL — ignoring it.");
+            return args;
+        }
+
+        internal static bool IsSafeBrandingImageUrl(string url)
+        {
+            if (string.IsNullOrEmpty(url) || url.Length > 2048)
+                return false;
+
+            foreach (var ch in url)
+            {
+                if (ch == '"' || ch == '\'' || char.IsWhiteSpace(ch) || char.IsControl(ch))
+                    return false;
+            }
+
+            return Uri.TryCreate(url, UriKind.Absolute, out var uri)
+                && uri.Scheme == Uri.UriSchemeHttps
+                && !string.IsNullOrEmpty(uri.Host);
+        }
+
         private static void TryCopy(string source, string destination)
         {
             try { if (File.Exists(source)) File.Copy(source, destination, overwrite: true); }

src/Backend/AutopilotMonitor.Functions.Tests/AuthFunctionSideEffectTests.cs

@@ -123,6 +123,22 @@ public class AuthFunctionSideEffectTests
     // HandleNewTenantDomainAsync
     // -------------------------------------------------------------------------
 
+    [Fact]
+    public async Task HandleNewTenantDomain_WhenUpnDomainIsNotAHostName_DoesNotSeed()
+    {
+        var config = DefaultConfig();
+        config.DomainName = null!;
+        config.OnboardedBy = null;
+
+        // The seed is rendered into transactional mails: anything but a strict host name is refused.
+        await _sut.HandleNewTenantDomainAsync(config, TenantId, "user@<b>contoso.com</b>");
+
+        Assert.True(string.IsNullOrEmpty(config.DomainName));
+        Assert.Null(config.OnboardedBy);
+        _tenantConfigMock.Verify(x => x.SaveConfigurationAsync(It.IsAny<TenantConfiguration>(), It.IsAny<string?>(), It.IsAny<string?>()), Times.Never);
+        _telegramMock.Verify(x => x.SendNewTenantSignupAsync(It.IsAny<string>(), It.IsAny<string>()), Times.Never);
+    }
+
     [Fact]
     public async Task HandleNewTenantDomain_WhenDomainEmpty_ExtractsAndSaves()
     {

src/Backend/AutopilotMonitor.Functions.Tests/BlobNameGuardTests.cs

@@ -0,0 +1,39 @@
+using AutopilotMonitor.Functions.Security;
+using Xunit;
+
+namespace AutopilotMonitor.Functions.Tests;
+
+/// <summary>
+/// Request-derived blob names must be flat. Azure.Storage.Blobs keeps '/' in the blob URI and
+/// System.Uri collapses '..' segments, so "x/../../other-container/y" would resolve outside the
+/// intended container. The guard is the last line at every GetBlobClient sink.
+/// </summary>
+public class BlobNameGuardTests
+{
+    [Theory]
+    [InlineData("11111111-1111-1111-1111-111111111111_aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa_diag_request_20260829_120000.zip")]
+    [InlineData("report.zip")]
+    [InlineData("a.b.c.zip")]
+    public void IsFlat_AcceptsFlatNames(string name)
+    {
+        Assert.True(BlobNameGuard.IsFlat(name));
+        Assert.Equal(name, BlobNameGuard.EnsureFlat(name, "name"));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    [InlineData("TA_x/../../hosted-diagnostics/victim/payload_diag_request_1.zip")]
+    [InlineData("a/b.zip")]
+    [InlineData("a\\b.zip")]
+    [InlineData("..zip")]
+    [InlineData("a%2F..%2Fb.zip")]
+    [InlineData("a?b.zip")]
+    [InlineData("a#b.zip")]
+    public void IsFlat_RejectsPathShapedNames(string? name)
+    {
+        Assert.False(BlobNameGuard.IsFlat(name));
+        Assert.Throws<ArgumentException>(() => BlobNameGuard.EnsureFlat(name, "name"));
+    }
+}

src/Backend/AutopilotMonitor.Functions.Tests/BrandingImageUrlValidationTests.cs

@@ -0,0 +1,68 @@
+using AutopilotMonitor.Functions.Helpers;
+using AutopilotMonitor.Shared.Models;
+using Xunit;
+
+namespace AutopilotMonitor.Functions.Tests
+{
+    /// <summary>
+    /// The enrollment-summary branding image URL is delivered verbatim to every enrolling device,
+    /// fetched from the signed-in user's session and spliced into the summary-dialog command line.
+    /// The server must therefore only ever persist a plain absolute HTTPS URL — a value with an
+    /// embedded quote or a non-HTTPS scheme must fail the config PUT/PATCH.
+    /// </summary>
+    public class BrandingImageUrlValidationTests
+    {
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData("   ")]
+        [InlineData("https://cdn.example/logo.png")]
+        [InlineData("https://cdn.example:8443/assets/logo.png?v=2&x=y")]
+        [InlineData("https://cdn.example/logo%20one.png")]
+        public void ValidateBrandingImageUrl_WellFormed_ReturnsNull(string? url)
+        {
+            Assert.Null(TenantConfigValidation.ValidateBrandingImageUrl(url));
+        }
+
+        [Theory]
+        [InlineData("x\" --status-file \"C:\\some\\file\" --timeout \"0", "quotes")]
+        [InlineData("https://cdn.example/logo.png\"", "quotes")]
+        [InlineData("https://cdn.example/lo'go.png", "quotes")]
+        [InlineData("https://cdn.example/logo.png --cleanup", "whitespace")]
+        [InlineData("https://cdn.example/logo.png\r\n", "whitespace")]
+        [InlineData("http://cdn.example/logo.png", "HTTPS")]
+        [InlineData("file:///C:/Windows/logo.png", "HTTPS")]
+        [InlineData("ftp://cdn.example/logo.png", "HTTPS")]
+        [InlineData("cdn.example/logo.png", "absolute URL")]
+        [InlineData("https://localhost/logo.png", "localhost")]
+        [InlineData("https://10.0.0.1/logo.png", "IP address")]
+        public void ValidateBrandingImageUrl_Malformed_Rejected(string url, string expectedFragment)
+        {
+            var error = TenantConfigValidation.ValidateBrandingImageUrl(url);
+            Assert.NotNull(error);
+            Assert.Contains(expectedFragment, error);
+        }
+
+        [Fact]
+        public void ValidateBrandingImageUrl_Overlong_Rejected()
+        {
+            var url = "https://cdn.example/" + new string('a', TenantConfigValidation.MaxBrandingImageUrlLength);
+            Assert.Contains("characters", TenantConfigValidation.ValidateBrandingImageUrl(url));
+        }
+
+        [Fact]
+        public void ValidateModel_RejectsInjectedBrandingUrl()
+        {
+            var existing = new TenantConfiguration();
+            var candidate = new TenantConfiguration
+            {
+                EnrollmentSummaryBrandingImageUrl = "x\" --status-file \"C:\\some\\file\" --timeout \"0",
+            };
+
+            var error = TenantConfigValidation.ValidateModel(candidate, existing, isGlobalAdmin: true);
+
+            Assert.NotNull(error);
+            Assert.StartsWith("Invalid enrollment summary branding image URL", error);
+        }
+    }
+}

src/Backend/AutopilotMonitor.Functions.Tests/EmailServiceTests.cs

@@ -247,6 +247,18 @@ public sealed class EmailServiceTests
         Assert.Contains("linkedin.com", html);
     }
 
+    [Fact]
+    public void BuiltInTemplates_HtmlEncodeDomain()
+    {
+        const string hostile = "<a href=\"https://evil.invalid\">x</a>";
+
+        foreach (var html in new[] { EmailTemplates.GetOffboardingFarewellHtml(hostile), EmailTemplates.GetPreviewApprovedHtml(hostile) })
+        {
+            Assert.DoesNotContain(hostile, html);
+            Assert.Contains("&lt;a href=&quot;https://evil.invalid&quot;&gt;x&lt;/a&gt;", html);
+        }
+    }
+
     [Fact]
     public void FarewellTemplate_EmptyDomain_FallsBackToGenericLabel()
     {

src/Backend/AutopilotMonitor.Functions.Tests/EmailTemplateServiceTests.cs

@@ -29,6 +29,30 @@ public sealed class EmailTemplateServiceTests
         Assert.DoesNotContain(EmailTemplateService.DomainPlaceholder, html);
     }
 
+    [Theory]
+    [InlineData("<b>x</b>", "&lt;b&gt;x&lt;/b&gt;")]
+    [InlineData("a\"b&c", "a&quot;b&amp;c")]
+    public void Render_HtmlEncodesDomain_ForOverrideTemplates(string domain, string expected)
+    {
+        var html = EmailTemplateService.Render("<p>{{domainName}}</p>", domain);
+
+        Assert.Equal($"<p>{expected}</p>", html);
+    }
+
+    [Theory]
+    [InlineData(EmailTemplateKind.Welcome)]
+    [InlineData(EmailTemplateKind.Farewell)]
+    public async Task BuiltIn_HtmlEncodesDomain_NoDoubleEncoding(EmailTemplateKind kind)
+    {
+        var (sut, _) = Build();
+
+        var html = await sut.GetHtmlAsync(kind, "<img src=x onerror=alert(1)>&\"");
+
+        Assert.DoesNotContain("<img", html);
+        Assert.Contains("&lt;img src=x onerror=alert(1)&gt;&amp;&quot;", html);
+        Assert.DoesNotContain("&amp;lt;", html);
+    }
+
     [Fact]
     public async Task Override_WinsAndRendersPlaceholder()
     {

src/Backend/AutopilotMonitor.Functions.Tests/HardwareWhitelistCsvIntegrityTests.cs

@@ -0,0 +1,102 @@
+using System.Linq;
+using AutopilotMonitor.Functions.Helpers;
+using AutopilotMonitor.Functions.Security;
+using AutopilotMonitor.Shared.Models;
+using Xunit;
+
+namespace AutopilotMonitor.Functions.Tests
+{
+    /// <summary>
+    /// The hardware whitelist is stored as one CSV and split at enforcement time. A value that
+    /// carries the delimiter (e.g. an attacker-chosen distress-signal manufacturer "Dell Inc.,*")
+    /// must never be able to widen the gate: the server rejects malformed lists and the parser
+    /// yields exactly the trimmed, non-empty items.
+    /// </summary>
+    public class HardwareWhitelistCsvIntegrityTests
+    {
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData("   ")]
+        [InlineData("*")]
+        [InlineData("Dell*,HP*,Lenovo*,Microsoft Corporation")]
+        [InlineData("Dell Inc.?*")]
+        [InlineData(" Dell* , HP* ")]
+        public void ValidateHardwareWhitelist_WellFormed_ReturnsNull(string? csv)
+        {
+            Assert.Null(TenantConfigValidation.ValidateHardwareWhitelist(csv));
+        }
+
+        [Theory]
+        [InlineData("Dell Inc.,")]
+        [InlineData(",Dell*")]
+        [InlineData("Dell*,,HP*")]
+        [InlineData("Dell*, ,HP*")]
+        [InlineData(",")]
+        public void ValidateHardwareWhitelist_BlankItem_Rejected(string csv)
+        {
+            var error = TenantConfigValidation.ValidateHardwareWhitelist(csv);
+            Assert.NotNull(error);
+            Assert.Contains("must not be empty", error);
+        }
+
+        [Fact]
+        public void ValidateHardwareWhitelist_ControlCharacter_Rejected()
+        {
+            var csv = "Dell*" + (char)1 + ",HP*";
+            Assert.Contains("control characters", TenantConfigValidation.ValidateHardwareWhitelist(csv));
+        }
+
+        [Fact]
+        public void ValidateHardwareWhitelist_OverlongEntry_Rejected()
+        {
+            Assert.Contains("128 characters",
+                TenantConfigValidation.ValidateHardwareWhitelist(new string('a', 129)));
+        }
+
+        [Fact]
+        public void ValidateHardwareWhitelist_TooManyEntries_Rejected()
+        {
+            var csv = string.Join(",", Enumerable.Repeat("x", 201));
+            Assert.Contains("200 entries", TenantConfigValidation.ValidateHardwareWhitelist(csv));
+        }
+
+        [Fact]
+        public void ValidateModel_RejectsMalformedWhitelists_WithFieldSpecificMessage()
+        {
+            var existing = TenantConfiguration.CreateDefault("tenant");
+
+            var badMfr = TenantConfiguration.CreateDefault("tenant");
+            badMfr.ManufacturerWhitelist = "Dell*,Dell Inc.,";
+            Assert.StartsWith("Invalid manufacturer whitelist:",
+                TenantConfigValidation.ValidateModel(badMfr, existing, isGlobalAdmin: false));
+
+            var badModel = TenantConfiguration.CreateDefault("tenant");
+            badModel.ModelWhitelist = "Latitude*,,";
+            Assert.StartsWith("Invalid model whitelist:",
+                TenantConfigValidation.ValidateModel(badModel, existing, isGlobalAdmin: false));
+
+            Assert.Null(TenantConfigValidation.ValidateModel(
+                TenantConfiguration.CreateDefault("tenant"), existing, isGlobalAdmin: false));
+        }
+
+        [Fact]
+        public void ParseWhitelist_TrimsEntries_SoEditorViewMatchesEnforcement()
+        {
+            // The web editor displays trimmed items; enforcement must match the same patterns.
+            Assert.Equal(new[] { "Dell*", "HP*" }, TenantConfiguration.ParseWhitelist("Dell*, HP*"));
+            Assert.Equal(new[] { "*" }, TenantConfiguration.ParseWhitelist(" "));
+        }
+
+        [Fact]
+        public void NeutralizedDistressValue_MatchesOnlyItself_NotEveryManufacturer()
+        {
+            // "Dell Inc.,*" neutralized by the web helper to the single pattern "Dell Inc.?*".
+            var whitelist = TenantConfiguration.ParseWhitelist("Dell*,Dell Inc.?*");
+            Assert.DoesNotContain("*", whitelist);
+
+            Assert.False(HardwareWhitelistValidator.ValidateHardware("Contoso", "X1", whitelist, new[] { "*" }).IsValid);
+            Assert.True(HardwareWhitelistValidator.ValidateHardware("Dell Inc.,*", "X1", whitelist, new[] { "*" }).IsValid);
+        }
+    }
+}

src/Backend/AutopilotMonitor.Functions.Tests/HostedDiagnosticsBlobServiceTests.cs

@@ -26,7 +26,9 @@ public class HostedDiagnosticsBlobServiceTests
 {
     private const string TenantA = "11111111-1111-1111-1111-111111111111";
     private const string TenantB = "22222222-2222-2222-2222-222222222222";
-    private const string Filename = "AgentDiagnostics-aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa-20260519T120000.zip";
+    private const string SessionA = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";
+    private const string SessionB = "bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb";
+    private const string Filename = "AgentDiagnostics-" + SessionA + "-20260519T120000.zip";
 
     // ── Path build + validation ────────────────────────────────────────────────────
 
@@ -89,7 +91,15 @@ public class HostedDiagnosticsBlobServiceTests
     {
         var svc = new FakeHostedDiagnosticsBlobService();
         await Assert.ThrowsAsync<ArgumentException>(
-            () => svc.GenerateUploadSasAsync("not-a-guid", Filename));
+            () => svc.GenerateUploadSasAsync("not-a-guid", SessionA, Filename));
+    }
+
+    [Fact]
+    public async Task GenerateUploadSas_RejectsNonGuidSessionId()
+    {
+        var svc = new FakeHostedDiagnosticsBlobService();
+        await Assert.ThrowsAsync<ArgumentException>(
+            () => svc.GenerateUploadSasAsync(TenantA, "not-a-guid", Filename));
     }
 
     [Fact]
@@ -97,14 +107,64 @@ public class HostedDiagnosticsBlobServiceTests
     {
         var svc = new FakeHostedDiagnosticsBlobService();
         await Assert.ThrowsAsync<ArgumentException>(
-            () => svc.GenerateUploadSasAsync(TenantA, "../other-tenant/escape.zip"));
+            () => svc.GenerateUploadSasAsync(TenantA, SessionA, "../other-tenant/escape.zip"));
+    }
+
+    // ── Session binding — one device must not be able to name another session's package ──
+
+    [Theory]
+    [InlineData("AgentDiagnostics-" + SessionB + "-20260519T120000.zip")]                 // foreign session
+    [InlineData("AgentDiagnostics-" + SessionA + "20260519T120000.zip")]                  // missing separator
+    [InlineData("AgentDiagnostics-" + SessionA + "-")]                                     // nothing after the session
+    [InlineData("AgentDiagnostics-" + SessionA + "-20260519T120000.txt")]                 // not a zip
+    [InlineData("x-AgentDiagnostics-" + SessionA + "-20260519T120000.zip")]               // wrong prefix
+    [InlineData("other.zip")]
+    public async Task GenerateUploadSas_RejectsFilenameNotBoundToSession(string filename)
+    {
+        var svc = new FakeHostedDiagnosticsBlobService();
+        await Assert.ThrowsAsync<ArgumentException>(
+            () => svc.GenerateUploadSasAsync(TenantA, SessionA, filename));
+        Assert.Empty(svc.CapturedSasBuilders);
+    }
+
+    [Theory]
+    [InlineData("AgentDiagnostics-" + SessionA + "-20260519T120000.zip")]
+    [InlineData("AgentDiagnostics-" + SessionA + "-20260519T120000-preprov.zip")]
+    [InlineData("AgentDiagnostics-" + SessionA + "-20260724170902-server-requested.zip")]
+    [InlineData("agentdiagnostics-" + SessionA + "-20260519T120000.ZIP")]                 // case-insensitive
+    public async Task GenerateUploadSas_AcceptsEveryAgentProducedShapeForOwnSession(string filename)
+    {
+        var svc = new FakeHostedDiagnosticsBlobService();
+        var result = await svc.GenerateUploadSasAsync(TenantA, SessionA, filename);
+        Assert.Equal($"{TenantA}/{filename}", result.BlobPath);
+    }
+
+    // ── Create-only — an existing blob is never re-issued ─────────────────────────
+
+    [Fact]
+    public async Task GenerateUploadSas_ExistingBlob_ThrowsAlreadyExists_AndMintsNothing()
+    {
+        var svc = new FakeHostedDiagnosticsBlobService { ExistingBlobPath = $"{TenantA}/{Filename}" };
+        var ex = await Assert.ThrowsAsync<HostedBlobAlreadyExistsException>(
+            () => svc.GenerateUploadSasAsync(TenantA, SessionA, Filename));
+        Assert.Equal($"{TenantA}/{Filename}", ex.BlobPath);
+        Assert.Empty(svc.CapturedSasBuilders);
+    }
+
+    [Fact]
+    public async Task GenerateUploadSas_ExistingBlobInOtherTenant_DoesNotBlockSameName()
+    {
+        // Existence is checked on the tenant-prefixed path, not on the bare filename.
+        var svc = new FakeHostedDiagnosticsBlobService { ExistingBlobPath = $"{TenantB}/{Filename}" };
+        var result = await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
+        Assert.Equal($"{TenantA}/{Filename}", result.BlobPath);
     }
 
     [Fact]
     public async Task GenerateUploadSas_ReturnsTenantPrefixedBlobPath()
     {
         var svc = new FakeHostedDiagnosticsBlobService();
-        var result = await svc.GenerateUploadSasAsync(TenantA, Filename);
+        var result = await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
         Assert.Equal($"{TenantA}/{Filename}", result.BlobPath);
     }
 
@@ -112,9 +172,9 @@ public class HostedDiagnosticsBlobServiceTests
     public async Task GenerateUploadSas_EnsuresContainerOnce()
     {
         var svc = new FakeHostedDiagnosticsBlobService();
-        await svc.GenerateUploadSasAsync(TenantA, Filename);
-        await svc.GenerateUploadSasAsync(TenantA, Filename);
-        await svc.GenerateUploadSasAsync(TenantB, "other.zip");
+        await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
+        await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
+        await svc.GenerateUploadSasAsync(TenantB, SessionA, Filename);
         Assert.Equal(1, svc.EnsureContainerCallCount);
     }
 
@@ -124,7 +184,7 @@ public class HostedDiagnosticsBlobServiceTests
         var svc = new FakeHostedDiagnosticsBlobService();
         var requested = TimeSpan.FromHours(24);
         var before = DateTime.UtcNow;
-        var result = await svc.GenerateUploadSasAsync(TenantA, Filename, requested);
+        var result = await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename, requested);
         var maxAllowed = before.Add(HostedDiagnosticsBlobService.MaxUploadSasTtl).AddMinutes(1); // tolerance
         Assert.True(result.ExpiresAt <= maxAllowed,
             $"ExpiresAt {result.ExpiresAt:O} exceeded MaxUploadSasTtl-bounded {maxAllowed:O}");
@@ -135,16 +195,16 @@ public class HostedDiagnosticsBlobServiceTests
     {
         var svc = new FakeHostedDiagnosticsBlobService();
         var before = DateTime.UtcNow;
-        var result = await svc.GenerateUploadSasAsync(TenantA, Filename);
+        var result = await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
         var delta = result.ExpiresAt - before;
         Assert.InRange(delta.TotalMinutes, 14, 16);
     }
 
     [Fact]
-    public async Task GenerateUploadSas_PassesBlobScopedResourceAndWriteCreateOnlyPermsToBuilder()
+    public async Task GenerateUploadSas_PassesBlobScopedResourceAndCreateOnlyPermsToBuilder()
     {
         var svc = new FakeHostedDiagnosticsBlobService();
-        await svc.GenerateUploadSasAsync(TenantA, Filename);
+        await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
 
         Assert.Single(svc.CapturedSasBuilders);
         var builder = svc.CapturedSasBuilders.Single();
@@ -152,24 +212,26 @@ public class HostedDiagnosticsBlobServiceTests
         Assert.Equal($"{TenantA}/{Filename}", builder.BlobName);
         Assert.Equal("diagnostics", builder.BlobContainerName);
 
-        // Reconstruct the permissions string to ensure ONLY Write + Create are set —
+        // ONLY Create — no Write (would allow replacing an existing same-tenant blob),
         // no Read (would expose other-tenant blobs in cross-tenant scenarios),
         // no Delete (cleanup is service-side via DeleteIfExistsAsync),
         // no List (agent has no enumeration need).
-        var permsString = builder.Permissions ?? string.Empty;
-        Assert.Contains("w", permsString);
-        Assert.Contains("c", permsString);
-        Assert.DoesNotContain("r", permsString);
-        Assert.DoesNotContain("d", permsString);
-        Assert.DoesNotContain("l", permsString);
+        Assert.Equal("c", builder.Permissions);
+    }
+
+    [Fact]
+    public void UploadSasPermissions_IsCreateOnly()
+    {
+        // Pinned: Write must never come back — it is what turns a create into an overwrite.
+        Assert.Equal(BlobSasPermissions.Create, HostedDiagnosticsBlobService.UploadSasPermissions);
     }
 
     [Fact]
     public async Task GenerateUploadSas_DifferentTenants_GetDifferentBlobPaths()
     {
         var svc = new FakeHostedDiagnosticsBlobService();
-        var a = await svc.GenerateUploadSasAsync(TenantA, Filename);
-        var b = await svc.GenerateUploadSasAsync(TenantB, Filename);
+        var a = await svc.GenerateUploadSasAsync(TenantA, SessionA, Filename);
+        var b = await svc.GenerateUploadSasAsync(TenantB, SessionA, Filename);
         Assert.NotEqual(a.BlobPath, b.BlobPath);
         Assert.StartsWith(TenantA + "/", a.BlobPath);
         Assert.StartsWith(TenantB + "/", b.BlobPath);
@@ -177,8 +239,6 @@ public class HostedDiagnosticsBlobServiceTests
 
     // ── DeleteBySessionPrefixAsync — cascade sweep for multi-package sessions ──────
 
-    private const string SessionA = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa";
-
     [Theory]
     [InlineData("not-a-guid", SessionA)]
     [InlineData(TenantA, "not-a-guid")]
@@ -310,6 +370,9 @@ public class HostedDiagnosticsBlobServiceTests
         public int EnsureContainerCallCount { get; private set; }
         public List<BlobSasBuilder> CapturedSasBuilders { get; } = new();
 
+        /// <summary>Blob path that the fake reports as already existing (null = nothing exists).</summary>
+        public string? ExistingBlobPath { get; set; }
+
         public FakeHostedDiagnosticsBlobService()
             : base(
                 new BlobServiceClient("UseDevelopmentStorage=true"),
@@ -324,6 +387,9 @@ public class HostedDiagnosticsBlobServiceTests
             return Task.CompletedTask;
         }
 
+        protected override Task<bool> BlobExistsAsync(string blobPath, CancellationToken cancellationToken)
+            => Task.FromResult(ExistingBlobPath == blobPath);
+
         protected override Task<Uri> BuildUploadSasUriAsync(
             string blobPath, DateTimeOffset expiresOn, CancellationToken cancellationToken)
         {
@@ -338,7 +404,7 @@ public class HostedDiagnosticsBlobServiceTests
                 StartsOn = DateTimeOffset.UtcNow.AddMinutes(-5),
                 ExpiresOn = expiresOn,
             };
-            builder.SetPermissions(BlobSasPermissions.Write | BlobSasPermissions.Create);
+            builder.SetPermissions(HostedDiagnosticsBlobService.UploadSasPermissions);
             CapturedSasBuilders.Add(builder);
 
             return Task.FromResult(new Uri($"https://fake.blob.core.windows.net/diagnostics/{blobPath}?fake=sas"));

src/Backend/AutopilotMonitor.Functions.Tests/PolicyEnforcementMiddlewareTests.cs

@@ -1308,4 +1308,119 @@ public class PolicyEnforcementMiddlewareTests
         Assert.True(result.Allowed);
         Assert.Equal(string.Empty, result.Context!.CallerId);
     }
+
+    // ── Tenant suspension gate (TenantConfiguration.Disabled / DisabledUntil) ──────────
+    // The operator kill-switch must revoke API access on the shared authorization path, not only
+    // on the SPA's auth/me probe — a direct REST caller with a valid token must get 403 too.
+
+    private static void AsSuspended(Harness h, string tenantId, DateTime? until = null, string? reason = null) =>
+        h.ConfigRepo.Setup(r => r.GetTenantConfigurationAsync(tenantId))
+            .ReturnsAsync(new TenantConfiguration
+            {
+                TenantId = tenantId,
+                Disabled = true,
+                DisabledUntil = until,
+                DisabledReason = reason,
+            });
+
+    [Fact]
+    public async Task Suspended_HomeTenant_ReadRoute_IsForbidden_WithTenantSuspendedCode()
+    {
+        const string upn = "admin@contoso.com";
+        var h = BuildHarness();
+        h.AsTenantAdmin(TenantA, upn);
+        AsSuspended(h, TenantA, until: DateTime.UtcNow.AddDays(30), reason: "Abuse investigation");
+
+        var result = await h.Middleware.DecideAsync("GET", "/api/sessions", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.False(result.Allowed);
+        Assert.Equal(403, result.StatusCode);
+        Assert.Equal("TenantSuspended", result.ErrorCode);
+        Assert.Equal("Abuse investigation", result.ErrorMessage);
+    }
+
+    [Fact]
+    public async Task Suspended_HomeTenant_WriteRoute_IsForbidden()
+    {
+        const string upn = "admin@contoso.com";
+        var h = BuildHarness();
+        h.AsTenantAdmin(TenantA, upn);
+        AsSuspended(h, TenantA); // indefinite suspension (no DisabledUntil)
+
+        var result = await h.Middleware.DecideAsync("PUT", $"/api/config/{TenantA}", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.False(result.Allowed);
+        Assert.Equal("TenantSuspended", result.ErrorCode);
+    }
+
+    [Fact]
+    public async Task Suspended_ExpiredDisabledUntil_IsAllowed()
+    {
+        const string upn = "admin@contoso.com";
+        var h = BuildHarness();
+        h.AsTenantAdmin(TenantA, upn);
+        AsSuspended(h, TenantA, until: DateTime.UtcNow.AddMinutes(-1)); // suspension window elapsed
+
+        var result = await h.Middleware.DecideAsync("GET", "/api/sessions", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.True(result.Allowed);
+    }
+
+    [Fact]
+    public async Task Suspended_GlobalAdmin_BypassesGate_ToAdministerTenant()
+    {
+        const string upn = "ga@platform.example";
+        var h = BuildHarness();
+        h.AsGlobalRole(Constants.GlobalRoles.GlobalAdmin);
+        AsSuspended(h, TenantA);
+        AsSuspended(h, TenantB);
+
+        var own = await h.Middleware.DecideAsync("GET", "/api/sessions", null, AuthedPrincipal(TenantA, upn));
+        var cross = await h.Middleware.DecideAsync("PUT", $"/api/config/{TenantB}", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.True(own.Allowed);
+        Assert.True(cross.Allowed);
+    }
+
+    [Fact]
+    public async Task Suspended_DelegatedReader_TargetTenantSuspended_IsForbidden()
+    {
+        const string upn = "msp@partner.example";
+        var h = BuildHarness();
+        h.AsDelegated(TenantB);
+        AsSuspended(h, TenantB); // home tenant A is fine, managed target B is suspended
+
+        var result = await h.Middleware.DecideAsync("GET", $"/api/config/{TenantB}", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.False(result.Allowed);
+        Assert.Equal("TenantSuspended", result.ErrorCode);
+    }
+
+    [Fact]
+    public async Task Suspended_DelegatedReader_HomeTenantSuspended_LosesDelegatedReach()
+    {
+        const string upn = "msp@partner.example";
+        var h = BuildHarness();
+        h.AsDelegated(TenantB);
+        AsSuspended(h, TenantA); // the MSP's own home tenant is suspended
+
+        var result = await h.Middleware.DecideAsync("GET", $"/api/config/{TenantB}", null, AuthedPrincipal(TenantA, upn));
+
+        Assert.False(result.Allowed);
+        Assert.Equal("TenantSuspended", result.ErrorCode);
+    }
+
+    [Fact]
+    public async Task Suspended_DeviceRoute_NoPrincipal_GateNotApplied()
+    {
+        // Anonymous/device routes carry no principal — SecurityValidator owns their tenant gate. The
+        // middleware must not touch tenant config here (no tenant to key on).
+        var h = BuildHarness();
+        AsSuspended(h, TenantA);
+
+        var result = await h.Middleware.DecideAsync("GET", "/api/health", null, null);
+
+        Assert.True(result.Allowed);
+        h.ConfigRepo.Verify(r => r.GetTenantConfigurationAsync(It.IsAny<string>()), Times.Never);
+    }
 }

src/Backend/AutopilotMonitor.Functions.Tests/SessionReportDiagnosticsArchiveCopierTests.cs

@@ -55,6 +55,23 @@ public class SessionReportDiagnosticsArchiveCopierTests
         Assert.Equal(0, copier.HostedOpenCalls + copier.CustomerOpenCalls + copier.UploadCalls);
     }
 
+    [Theory]
+    [InlineData("x/../../hosted-diagnostics/22222222-2222-2222-2222-222222222222/payload_diag_archive_1.zip")]
+    [InlineData("sub/dir_diag_archive_1.zip")]
+    [InlineData("..\\escape_diag_archive_1.zip")]
+    public async Task CopyAsync_NonFlatDestination_Rejected_WithoutReadOrWrite(string destination)
+    {
+        // A path-shaped destination would let the SDK + System.Uri resolve the write outside
+        // the session-reports container. Reject before touching any storage.
+        var copier = new RecordingCopier();
+
+        var result = await copier.CopyAsync(TenantA, SessionId, HostedBlob, destination);
+
+        Assert.False(result.Success);
+        Assert.Equal(SessionReportDiagnosticsArchiveCopier.Statuses.FailedInvalidBlobName, result.Status);
+        Assert.Equal(0, copier.HostedOpenCalls + copier.CustomerOpenCalls + copier.UploadCalls);
+    }
+
     [Fact]
     public async Task CopyAsync_Hosted_HappyPath_UploadsWithFlatName()
     {

src/Backend/AutopilotMonitor.Functions.Tests/TenantContactEmailTests.cs

@@ -1,11 +1,13 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Azure;
 using Azure.Data.Tables;
 using AutopilotMonitor.Functions.DataAccess.TableStorage;
 using AutopilotMonitor.Functions.Functions.Config;
+using AutopilotMonitor.Functions.Helpers;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared;
 using AutopilotMonitor.Shared.DataAccess;
@@ -386,4 +388,40 @@ public class TenantContactEmailTests
             It.IsAny<string>(), It.IsAny<string>(),
             It.IsAny<IEnumerable<string>>(), It.IsAny<CancellationToken>()), Times.Never);
     }
+
+    // -------------------------------------------------------------------------
+    // IsValidDomainName — the only shape DomainName may be persisted in
+    // -------------------------------------------------------------------------
+
+    [Theory]
+    [InlineData("contoso.com")]
+    [InlineData("sub.domain.org")]
+    [InlineData("x-y.example")]
+    [InlineData("A1.B2.c3")]
+    public void IsValidDomainName_AcceptsHostNames(string domain)
+        => Assert.True(TenantConfigValidation.IsValidDomainName(domain));
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("localhost")]
+    [InlineData(".contoso.com")]
+    [InlineData("contoso.com.")]
+    [InlineData("con..toso.com")]
+    [InlineData("-contoso.com")]
+    [InlineData("contoso-.com")]
+    [InlineData("con toso.com")]
+    [InlineData("<b>contoso.com</b>")]
+    [InlineData("contoso.com\"onerror=\"x")]
+    [InlineData("contoso.com/path")]
+    [InlineData("user@contoso.com")]
+    public void IsValidDomainName_RejectsNonHostNames(string? domain)
+        => Assert.False(TenantConfigValidation.IsValidDomainName(domain));
+
+    [Fact]
+    public void IsValidDomainName_RejectsOverlongNamesAndLabels()
+    {
+        Assert.False(TenantConfigValidation.IsValidDomainName(new string('a', 64) + ".com"));
+        Assert.False(TenantConfigValidation.IsValidDomainName(string.Join(".", Enumerable.Repeat(new string('a', 60), 5))));
+    }
 }

src/Backend/AutopilotMonitor.Functions/Functions/Config/UpdateTenantConfigurationFunction.cs

@@ -110,6 +110,12 @@ namespace AutopilotMonitor.Functions.Functions.Config
                 // admins are served the FULL config so this is normally a no-op for them.)
                 config.RestoreRedactedSecretsFrom(existingConfig);
 
+                // DomainName is tenant identity: seeded once from the first login's UPN (AuthFunction)
+                // and never client-writable — for ANY caller, GA included — mirroring the patch flow
+                // ("identity — never writable"). Without this preserve the full-model PUT persisted an
+                // arbitrary string here, which is rendered into the welcome/farewell mails.
+                config.DomainName = existingConfig.DomainName;
+
                 // Shared model validation (rate limits, contact address, webhook/Teams SSRF, custom
                 // headers, notification channels, diagnostics SAS, retention cap) — single source
                 // with the transactional field-patch flow (TenantConfigValidation).

src/Backend/AutopilotMonitor.Functions/Functions/Diagnostics/GetDiagnosticsUploadUrlFunction.cs

@@ -2,6 +2,7 @@
 using System.Web;
 using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
+using AutopilotMonitor.Functions.Services.Deletion;
 using AutopilotMonitor.Functions.Services.Diagnostics;
 using AutopilotMonitor.Shared.Models;
 using Microsoft.Azure.Functions.Worker;
@@ -19,8 +20,10 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
     ///         container SAS URL stored in <see cref="TenantConfiguration.DiagnosticsBlobSasUrl"/>.
     ///         Data stays in the customer's own storage account.</item>
     ///   <item><c>Hosted</c> (opt-in): mints a freshly-stamped, 15-min, blob-scoped,
-    ///         Write+Create-only SAS pinned to <c>{tenantId}/{filename}</c> in the backend's
-    ///         own diagnostics container. Requires explicit admin opt-in via the UI; never
+    ///         Create-only SAS pinned to <c>{tenantId}/{filename}</c> in the backend's
+    ///         own diagnostics container. The filename must carry the requesting session id
+    ///         and the blob must not exist yet, so one device can neither name nor replace
+    ///         another session's package. Requires explicit admin opt-in via the UI; never
     ///         silent.</item>
     /// </list>
     /// Called by the agent just before uploading — never at startup, never cached.
@@ -56,6 +59,8 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
         private readonly IntuneDeviceBindingValidator _intuneDeviceBindingValidator;
         private readonly BootstrapSessionService _bootstrapSessionService;
         private readonly HostedDiagnosticsBlobService _hostedDiagnostics;
+        private readonly ISessionDeletionInventoryReader _sessionRowReader;
+        private readonly SessionOwnerBindingObserver _ownerBinding;
 
         public GetDiagnosticsUploadUrlFunction(
             ILogger<GetDiagnosticsUploadUrlFunction> logger,
@@ -68,8 +73,12 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
             CloudPcDeviceValidator cloudPcDeviceValidator,
             IntuneDeviceBindingValidator intuneDeviceBindingValidator,
             BootstrapSessionService bootstrapSessionService,
-            HostedDiagnosticsBlobService hostedDiagnostics)
+            HostedDiagnosticsBlobService hostedDiagnostics,
+            ISessionDeletionInventoryReader sessionRowReader,
+            SessionOwnerBindingObserver ownerBinding)
         {
+            _sessionRowReader = sessionRowReader;
+            _ownerBinding = ownerBinding;
             _logger = logger;
             _configService = configService;
             _adminConfigService = adminConfigService;
@@ -145,7 +154,7 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
 
                 if (destination == DestinationHosted)
                 {
-                    return await IssueHostedSasAsync(req, requestBody);
+                    return await IssueHostedSasAsync(req, requestBody, validation);
                 }
 
                 if (destination == DestinationCustomerSas)
@@ -237,7 +246,7 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
         }
 
         private async Task<HttpResponseData> IssueHostedSasAsync(
-            HttpRequestData req, GetDiagnosticsUploadUrlRequest requestBody)
+            HttpRequestData req, GetDiagnosticsUploadUrlRequest requestBody, SecurityValidationResult validation)
         {
             if (string.IsNullOrEmpty(requestBody.FileName))
             {
@@ -250,18 +259,36 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
                 return badRequest;
             }
 
+            // The blob name is bound to the session below, so the session id has to be a real
+            // one — and it is the coordinate for the owner-binding observation.
+            if (!SecurityValidator.IsValidGuid(requestBody.SessionId))
+            {
+                var badRequest = req.CreateResponse(HttpStatusCode.BadRequest);
+                await badRequest.WriteAsJsonAsync(new GetDiagnosticsUploadUrlResponse
+                {
+                    Success = false,
+                    Message = "sessionId is required for hosted destination"
+                });
+                return badRequest;
+            }
+
+            // SESSION-OWNER-BINDING-SHADOW: same observation as the session-scoped writes, so
+            // stage-2 enforcement covers this endpoint with the same data. Never rejects here.
+            await ObserveSessionOwnerAsync(req, requestBody.TenantId, requestBody.SessionId, validation);
+
             HostedUploadSasResult sasResult;
             try
             {
                 sasResult = await _hostedDiagnostics.GenerateUploadSasAsync(
-                    requestBody.TenantId, requestBody.FileName);
+                    requestBody.TenantId, requestBody.SessionId, requestBody.FileName);
             }
             catch (ArgumentException ex)
             {
-                // Filename validation failed (path separator, traversal, oversize, etc.)
+                // Filename validation failed (path separator, traversal, oversize, not bound
+                // to the requesting session, etc.)
                 _logger.LogWarning(
-                    "GetDiagnosticsUploadUrl: rejecting hosted SAS for tenant {TenantId}, file {FileName}: {Reason}",
-                    requestBody.TenantId, requestBody.FileName, ex.Message);
+                    "GetDiagnosticsUploadUrl: rejecting hosted SAS for tenant {TenantId}, session {SessionId}, file {FileName}: {Reason}",
+                    requestBody.TenantId, requestBody.SessionId, requestBody.FileName, ex.Message);
                 var badRequest = req.CreateResponse(HttpStatusCode.BadRequest);
                 await badRequest.WriteAsJsonAsync(new GetDiagnosticsUploadUrlResponse
                 {
@@ -270,6 +297,21 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
                 });
                 return badRequest;
             }
+            catch (HostedBlobAlreadyExistsException ex)
+            {
+                // A legitimate agent never re-requests an existing name (every package is
+                // freshly timestamped); this is either a replay or an overwrite attempt.
+                _logger.LogWarning(
+                    "GetDiagnosticsUploadUrl: rejecting hosted SAS for tenant {TenantId}, session {SessionId}: blob {BlobPath} already exists",
+                    requestBody.TenantId, requestBody.SessionId, ex.BlobPath);
+                var conflict = req.CreateResponse(HttpStatusCode.Conflict);
+                await conflict.WriteAsJsonAsync(new GetDiagnosticsUploadUrlResponse
+                {
+                    Success = false,
+                    Message = "A diagnostics package with this name already exists"
+                });
+                return conflict;
+            }
 
             _logger.LogInformation(
                 "GetDiagnosticsUploadUrl: Issuing Hosted upload URL for tenant {TenantId}, session {SessionId}, blob {BlobPath}, SAS expires {ExpiresAt}",
@@ -288,6 +330,21 @@ namespace AutopilotMonitor.Functions.Functions.Diagnostics
             return response;
         }
 
+        private async Task ObserveSessionOwnerAsync(
+            HttpRequestData req, string tenantId, string sessionId, SecurityValidationResult validation)
+        {
+            try
+            {
+                var row = await _sessionRowReader.GetSessionRowAsync(tenantId, sessionId);
+                _ownerBinding.Observe(req, tenantId, sessionId, row, validation, "agent/upload-url");
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex,
+                    "GetDiagnosticsUploadUrl: session-owner observation skipped for session {SessionId}", sessionId);
+            }
+        }
+
         /// <summary>
         /// Normalizes the destination string from TenantConfiguration. Null/empty becomes
         /// CustomerSas (preserves existing behaviour for tenants that predate this field).

src/Backend/AutopilotMonitor.Functions/Functions/Infrastructure/AuthFunction.cs

@@ -2,6 +2,7 @@ using System.Collections.Generic;
 using System.Net;
 using AutopilotMonitor.Functions.Extensions;
 using AutopilotMonitor.Functions.Functions.Admin;
+using AutopilotMonitor.Functions.Helpers;
 using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared;
@@ -336,6 +337,14 @@ public class AuthFunction
         if (string.IsNullOrEmpty(domain))
             return;
 
+        // The seeded value is rendered into transactional mails — persist only a strict host name,
+        // regardless of what the identity provider's UPN charset happens to allow.
+        if (!TenantConfigValidation.IsValidDomainName(domain))
+        {
+            _logger.LogWarning("Refusing to seed DomainName for tenant {TenantId}: UPN domain is not a valid host name", tenantId);
+            return;
+        }
+
         _logger.LogInformation("Setting domain name for tenant {TenantId}: {Domain}", tenantId, domain);
         tenantConfig.DomainName = domain;
         tenantConfig.UpdatedBy = upn;

src/Backend/AutopilotMonitor.Functions/Functions/Reports/GetSessionReportDownloadUrlFunction.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using System.Web;
+using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using Microsoft.Azure.Functions.Worker;
 using Microsoft.Azure.Functions.Worker.Http;
@@ -44,7 +45,7 @@ namespace AutopilotMonitor.Functions.Functions.Reports
                 }
 
                 // Prevent path traversal
-                if (blobName.Contains("..") || blobName.Contains("/") || blobName.Contains("\\"))
+                if (!BlobNameGuard.IsFlat(blobName))
                 {
                     var badRequest = req.CreateResponse(HttpStatusCode.BadRequest);
                     await badRequest.WriteAsJsonAsync(new { success = false, message = "Invalid blob name." });

src/Backend/AutopilotMonitor.Functions/Functions/Reports/SubmitDiagFilesReportFunction.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using AutopilotMonitor.Functions.Helpers;
+using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared.DataAccess;
 using AutopilotMonitor.Shared.Models;
@@ -106,6 +107,14 @@ namespace AutopilotMonitor.Functions.Functions.Reports
                     return bad;
                 }
 
+                // TenantId becomes part of the blob name — must be a GUID, never path-shaped.
+                if (!SecurityValidator.IsValidGuid(request.TenantId))
+                {
+                    var invalid = req.CreateResponse(HttpStatusCode.BadRequest);
+                    await invalid.WriteAsJsonAsync(new { success = false, message = "Invalid tenantId." });
+                    return invalid;
+                }
+
                 var metadata = await _sessionReportService.SubmitDiagFilesReportAsync(request, userIdentifier);
 
                 // Audit log — skip for Global Admins (their actions are not tenant-scoped)

src/Backend/AutopilotMonitor.Functions/Functions/Reports/SubmitSessionReportFunction.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using AutopilotMonitor.Functions.Helpers;
+using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared.DataAccess;
 using AutopilotMonitor.Shared.Models;
@@ -105,6 +106,19 @@ namespace AutopilotMonitor.Functions.Functions.Reports
                     return bad;
                 }
 
+                // Identifier format gate: both values become part of the report blob name.
+                // Route values are percent-decoded, so an encoded '/' or '..' would otherwise
+                // reach the storage layer as a path segment.
+                if (!SecurityValidator.IsValidGuid(request.SessionId) || !SecurityValidator.IsValidGuid(request.TenantId))
+                {
+                    _logger.LogWarning(
+                        "SubmitSessionReport: BLOCKED non-GUID identifier user={User} tenant={TenantId} sessionIdLength={SessionIdLength}",
+                        userIdentifier, request.TenantId, request.SessionId?.Length ?? 0);
+                    var invalid = req.CreateResponse(HttpStatusCode.BadRequest);
+                    await invalid.WriteAsJsonAsync(new { success = false, message = "Invalid sessionId or tenantId." });
+                    return invalid;
+                }
+
                 // Submit report
                 var metadata = await _sessionReportService.SubmitReportAsync(request, userIdentifier);
 

src/Backend/AutopilotMonitor.Functions/Helpers/TenantConfigValidation.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared.Models;
+using AutopilotMonitor.Shared.Models.Config;
 
 namespace AutopilotMonitor.Functions.Helpers
 {
@@ -21,6 +22,120 @@ namespace AutopilotMonitor.Functions.Helpers
         // RFC 5321 caps a forward path at 254 characters.
         internal const int MaxContactEmailLength = 254;
 
+        // RFC 1035: a host name is at most 253 characters, labels at most 63.
+        internal const int MaxDomainNameLength = 253;
+
+        /// <summary>
+        /// True when <paramref name="domainName"/> is a strict DNS host name: dotted labels of
+        /// ASCII letters, digits and inner hyphens only. This is the ONLY shape DomainName may
+        /// ever be persisted in — it is rendered into transactional mails and admin views.
+        /// </summary>
+        internal static bool IsValidDomainName(string? domainName)
+        {
+            if (string.IsNullOrEmpty(domainName) || domainName.Length > MaxDomainNameLength)
+                return false;
+
+            var labels = domainName.Split('.');
+            if (labels.Length < 2)
+                return false;
+
+            foreach (var label in labels)
+            {
+                if (label.Length == 0 || label.Length > 63)
+                    return false;
+                if (label[0] == '-' || label[label.Length - 1] == '-')
+                    return false;
+                foreach (var ch in label)
+                {
+                    var ok = (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || ch == '-';
+                    if (!ok)
+                        return false;
+                }
+            }
+
+            return true;
+        }
+
+        private const int MaxWhitelistEntries = 200;
+        private const int MaxWhitelistEntryLength = 128;
+
+        /// <summary>
+        /// Validates a hardware whitelist CSV (<see cref="TenantConfiguration.ManufacturerWhitelist"/> /
+        /// <see cref="TenantConfiguration.ModelWhitelist"/>). The CSV is split on ',' at enforcement
+        /// time, so this is the last line of defence against a value that was meant as ONE entry but
+        /// alters the list structure: blank items (",,", ", ,") are rejected rather than silently
+        /// dropped, and every item must be a printable, bounded pattern. Returns a user-facing
+        /// reason, or null when the list is well-formed. Empty/whitespace = allow all (documented).
+        /// </summary>
+        internal static string? ValidateHardwareWhitelist(string? csv)
+        {
+            if (string.IsNullOrWhiteSpace(csv))
+                return null;
+
+            var items = csv!.Split(',');
+            if (items.Length > MaxWhitelistEntries)
+                return $"at most {MaxWhitelistEntries} entries are allowed.";
+
+            foreach (var raw in items)
+            {
+                var entry = raw.Trim();
+                if (entry.Length == 0)
+                    return "entries must not be empty (check for a stray or doubled comma).";
+                if (entry.Length > MaxWhitelistEntryLength)
+                    return $"each entry must be at most {MaxWhitelistEntryLength} characters.";
+                foreach (var ch in entry)
+                {
+                    if (char.IsControl(ch))
+                        return "entries must not contain control characters.";
+                }
+            }
+
+            return null;
+        }
+
+        // Generous for a CDN asset URL; bounds the command line the agent composes from it.
+        internal const int MaxBrandingImageUrlLength = 2048;
+
+        /// <summary>
+        /// Validates <see cref="TenantConfiguration.EnrollmentSummaryBrandingImageUrl"/>. The value
+        /// is delivered verbatim to every enrolling device, fetched from the signed-in user's
+        /// session and spliced into the summary-dialog command line, so it is the one piece of
+        /// tenant config that is both a device egress target and a process argument. It must be a
+        /// plain absolute HTTPS URL to a DNS host — no quotes, whitespace or control characters
+        /// that could terminate a quoted argument. Returns an error message, or null when
+        /// valid/empty (empty = no branding image).
+        /// </summary>
+        internal static string? ValidateBrandingImageUrl(string? url)
+        {
+            if (string.IsNullOrWhiteSpace(url))
+                return null;
+
+            if (url!.Length > MaxBrandingImageUrlLength)
+                return $"must be at most {MaxBrandingImageUrlLength} characters.";
+
+            foreach (var ch in url)
+            {
+                if (char.IsControl(ch) || char.IsWhiteSpace(ch))
+                    return "must not contain whitespace or control characters.";
+                if (ch == '"' || ch == '\'')
+                    return "must not contain quotes.";
+            }
+
+            if (!Uri.TryCreate(url, UriKind.Absolute, out var uri))
+                return "is not a valid absolute URL.";
+
+            if (uri.Scheme != Uri.UriSchemeHttps)
+                return "must use HTTPS.";
+
+            if (uri.IsLoopback || string.IsNullOrEmpty(uri.Host))
+                return "must not target localhost.";
+
+            if (System.Net.IPAddress.TryParse(uri.Host, out _))
+                return "must use a DNS hostname, not an IP address.";
+
+            return null;
+        }
+
         /// <summary>
         /// Validates a candidate configuration against the stored one. Returns a
         /// user-facing error message (same wording the PUT endpoint always produced),
@@ -58,6 +173,18 @@ namespace AutopilotMonitor.Functions.Helpers
             if (channelsError != null)
                 return $"Invalid notification channels: {channelsError}";
 
+            var brandingUrlError = ValidateBrandingImageUrl(candidate.EnrollmentSummaryBrandingImageUrl);
+            if (brandingUrlError != null)
+                return $"Invalid enrollment summary branding image URL: {brandingUrlError}";
+
+            var manufacturerWhitelistError = ValidateHardwareWhitelist(candidate.ManufacturerWhitelist);
+            if (manufacturerWhitelistError != null)
+                return $"Invalid manufacturer whitelist: {manufacturerWhitelistError}";
+
+            var modelWhitelistError = ValidateHardwareWhitelist(candidate.ModelWhitelist);
+            if (modelWhitelistError != null)
+                return $"Invalid model whitelist: {modelWhitelistError}";
+
             // Only validate the customer-supplied SAS URL when the tenant has actually selected
             // the CustomerSas destination — a stale value left over from a prior CustomerSas
             // configuration must not block a Hosted save (mirrors GetDiagnosticsUploadUrlFunction).

src/Backend/AutopilotMonitor.Functions/Middleware/PolicyEnforcementMiddleware.cs

@@ -5,6 +5,7 @@ using AutopilotMonitor.Functions.Helpers;
 using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services;
 using AutopilotMonitor.Shared;
+using AutopilotMonitor.Shared.Models;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Azure.Functions.Worker;
 using Microsoft.Azure.Functions.Worker.Middleware;
@@ -212,6 +213,29 @@ public class PolicyEnforcementMiddleware : IFunctionsWorkerMiddleware
                 decision.UserIdentifier, decision.UserRole, "CrossTenant");
         }
 
+        // Tenant suspension gate — the operator kill-switch (TenantConfiguration.Disabled/DisabledUntil) and
+        // the offboarding tombstone. Enforced HERE, on the shared authorization path, so it covers every
+        // tenant-scoped API call and not just the SPA's auth/me login probe (which also carries it, for the
+        // richer client payload). Both the caller's HOME tenant (JWT tid) and the request's TARGET tenant are
+        // checked: a suspended tenant's members lose everything, including delegated reach into other tenants,
+        // and nobody without platform scope reaches a suspended target. Platform operators (GA/Reader) bypass —
+        // they must still administer the suspended tenant. Anonymous/device routes bring their own gate
+        // (SecurityValidator → 403 TenantDisabled). Cached, side-effect-free read; a missing row is not disabled.
+        if (principal != null && !hasGlobalScope)
+        {
+            var suspended = await FindSuspendedTenantAsync(jwtTenantId, targetTenantId);
+            if (suspended != null)
+            {
+                _logger.LogWarning("[PolicyEnforcement] BLOCKED suspended tenant: user={User} tenant={Tenant} path={Path}",
+                    LogSanitizer.Clean(decision.UserIdentifier), LogSanitizer.Clean(suspended.TenantId), logPath);
+                return PolicyResult.Deny((int)HttpStatusCode.Forbidden, "TenantSuspended",
+                    !string.IsNullOrEmpty(suspended.DisabledReason)
+                        ? suspended.DisabledReason
+                        : "Your tenant has been suspended. Please contact support for more information.",
+                    decision.UserIdentifier, decision.UserRole, "TenantSuspended");
+            }
+        }
+
         // Merge delegated state from the two delegated admission paths:
         //  • scoped-route (RouteParam/QueryParam): a single-tenant cross-tenant read — delegatedRole +
         //    allowedTenantIds were set above.
@@ -259,6 +283,26 @@ public class PolicyEnforcementMiddleware : IFunctionsWorkerMiddleware
         return PolicyResult.Allow(requestContext, decision.UserIdentifier, decision.UserRole);
     }
 
+    /// <summary>
+    /// Returns the configuration of the first currently-suspended tenant among the caller's home tenant and
+    /// the request target (null when neither is suspended). <see cref="TenantConfigurationService.TryGetConfigurationAsync"/>
+    /// is cached (5 min TTL, same as the agent gate) and never persists a default row.
+    /// <see cref="TenantConfiguration.IsCurrentlyDisabled"/> already treats an elapsed DisabledUntil as
+    /// re-enabled, so the gate lifts on its own; auth/me persists the flip on the next login.
+    /// </summary>
+    private async Task<TenantConfiguration?> FindSuspendedTenantAsync(string jwtTenantId, string targetTenantId)
+    {
+        var (homeConfig, _) = await _tenantConfigService.TryGetConfigurationAsync(jwtTenantId);
+        if (homeConfig.IsCurrentlyDisabled())
+            return homeConfig;
+
+        if (string.Equals(targetTenantId, jwtTenantId, StringComparison.OrdinalIgnoreCase))
+            return null;
+
+        var (targetConfig, _) = await _tenantConfigService.TryGetConfigurationAsync(targetTenantId);
+        return targetConfig.IsCurrentlyDisabled() ? targetConfig : null;
+    }
+
     /// <summary>
     /// Resolves the request's target tenant. Returns the effective TargetTenantId (defaults to the JWT
     /// tenant) and the explicitly-named tenant from the route/query (null when the route does not name one,

src/Backend/AutopilotMonitor.Functions/Security/BlobNameGuard.cs

@@ -0,0 +1,28 @@
+namespace AutopilotMonitor.Functions.Security
+{
+    /// <summary>
+    /// Last-line guard for request-derived blob names. Azure.Storage.Blobs appends the name to
+    /// the container URI preserving '/' and System.Uri collapses '..' segments, so a name such as
+    /// "x/../../other-container/y" resolves OUTSIDE the intended container. Every blob name that
+    /// contains caller-influenced material must be flat: no separators, no dot segments.
+    /// </summary>
+    public static class BlobNameGuard
+    {
+        public static bool IsFlat(string? blobName)
+        {
+            if (string.IsNullOrWhiteSpace(blobName)) return false;
+            if (blobName.Contains('/') || blobName.Contains('\\')) return false;
+            if (blobName.Contains("..")) return false;
+            if (blobName.Contains('%') || blobName.Contains('?') || blobName.Contains('#')) return false;
+            return true;
+        }
+
+        /// <summary>Throws <see cref="ArgumentException"/> when the name is not flat.</summary>
+        public static string EnsureFlat(string? blobName, string parameterName)
+        {
+            if (!IsFlat(blobName))
+                throw new ArgumentException("Blob name must be a flat name without path separators or dot segments.", parameterName);
+            return blobName!;
+        }
+    }
+}

src/Backend/AutopilotMonitor.Functions/Services/Diagnostics/HostedDiagnosticsBlobService.cs

@@ -27,8 +27,8 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
     /// (<c>AzureStorageAccountName</c>) or connection string (<c>AzureBlobStorageConnectionString</c>).
     /// SAS issuance for the agent upload-url endpoint differs by auth path — User
     /// Delegation SAS under MI, account-key SAS under connection-string — both produce
-    /// a blob-scoped, Write+Create-only, 15-min token that cannot reach other tenants'
-    /// prefixes.
+    /// a blob-scoped, Create-only, 15-min token that cannot reach other tenants'
+    /// prefixes and cannot replace an existing blob.
     /// </para>
     /// </summary>
     public class HostedDiagnosticsBlobService
@@ -40,6 +40,16 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
         // requesting hour-long tokens.
         public static readonly TimeSpan MaxUploadSasTtl = TimeSpan.FromMinutes(60);
 
+        /// <summary>
+        /// Permissions on the upload SAS. Create-only by design: the agent PUTs one new block
+        /// blob per package (fresh timestamped name), so Write — which would allow replacing an
+        /// existing blob under the same tenant prefix — is never needed.
+        /// </summary>
+        public const BlobSasPermissions UploadSasPermissions = BlobSasPermissions.Create;
+
+        /// <summary>Canonical package-name prefix; the session id follows immediately after.</summary>
+        internal const string PackageNamePrefix = "AgentDiagnostics-";
+
         private readonly BlobServiceClient _blobServiceClient;
         private readonly ILogger<HostedDiagnosticsBlobService> _logger;
         private readonly bool _usesManagedIdentity;
@@ -94,16 +104,21 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
         // -------- Public API --------
 
         /// <summary>
-        /// Mints a blob-scoped, Write+Create-only SAS URI pinned to the EXACT path
+        /// Mints a blob-scoped, Create-only SAS URI pinned to the EXACT path
         /// <c>{tenantId}/{filename}</c> for an agent's diagnostics-package upload. Cannot
-        /// be redirected to other tenants' prefixes. TTL is capped at
-        /// <see cref="MaxUploadSasTtl"/> to keep the exposure window tight.
+        /// be redirected to other tenants' prefixes, and the filename must carry the
+        /// caller's <paramref name="sessionId"/> (<c>AgentDiagnostics-{sessionId}-…zip</c>)
+        /// so one device cannot name another session's package. An already-existing blob
+        /// is never re-issued (<see cref="HostedBlobAlreadyExistsException"/>). TTL is
+        /// capped at <see cref="MaxUploadSasTtl"/> to keep the exposure window tight.
         /// </summary>
         public virtual async Task<HostedUploadSasResult> GenerateUploadSasAsync(
-            string tenantId, string filename, TimeSpan? ttl = null, CancellationToken cancellationToken = default)
+            string tenantId, string sessionId, string filename, TimeSpan? ttl = null, CancellationToken cancellationToken = default)
         {
             SecurityValidator.EnsureValidGuid(tenantId, nameof(tenantId));
+            SecurityValidator.EnsureValidGuid(sessionId, nameof(sessionId));
             ValidateFilename(filename);
+            EnsureFilenameBoundToSession(filename, sessionId);
 
             var effectiveTtl = ttl ?? TimeSpan.FromMinutes(15);
             if (effectiveTtl > MaxUploadSasTtl)
@@ -116,6 +131,14 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
 
             await EnsureContainerAsync(cancellationToken);
 
+            // Create-only semantics, enforced twice: the SAS carries no Write permission (an
+            // existing blob cannot be replaced with it), and issuance itself refuses a name
+            // that is already taken so the conflict surfaces here as a 409 instead of as an
+            // opaque 403 from storage. Every package gets a fresh timestamped name, so a
+            // legitimate agent never asks for an existing one.
+            if (await BlobExistsAsync(blobPath, cancellationToken))
+                throw new HostedBlobAlreadyExistsException(blobPath);
+
             var sasUri = await BuildUploadSasUriAsync(blobPath, expiresOn, cancellationToken);
 
             return new HostedUploadSasResult
@@ -185,7 +208,7 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
 
             // Trailing dash bounds the match to this exact session id (GUIDs are fixed-length,
             // but the explicit separator keeps the invariant obvious and layout-proof).
-            var prefix = $"{tenantId}/AgentDiagnostics-{sessionId}-";
+            var prefix = $"{tenantId}/{PackageNamePrefix}{sessionId}-";
             var deleted = 0;
             await foreach (var item in containerClient.GetBlobsAsync(
                 BlobTraits.None, BlobStates.None, prefix: prefix, cancellationToken: cancellationToken))
@@ -272,7 +295,17 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
         }
 
         /// <summary>
-        /// Builds the blob-scoped Write+Create-only SAS URI for upload. Branch on the
+        /// Test seam: whether a blob already exists at <paramref name="blobPath"/>. Production
+        /// issues a HEAD; tests override to simulate a taken name without Azurite.
+        /// </summary>
+        protected virtual async Task<bool> BlobExistsAsync(string blobPath, CancellationToken cancellationToken)
+        {
+            var response = await GetContainerClient().GetBlobClient(blobPath).ExistsAsync(cancellationToken);
+            return response.Value;
+        }
+
+        /// <summary>
+        /// Builds the blob-scoped Create-only SAS URI for upload. Branch on the
         /// auth mode: MI uses User Delegation SAS (no account key needed); connection
         /// string uses the underlying StorageSharedKeyCredential via
         /// <see cref="BlobClient.GenerateSasUri(BlobSasBuilder)"/>.
@@ -290,9 +323,10 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
                 StartsOn = DateTimeOffset.UtcNow.AddMinutes(-5), // clock-skew tolerance
                 ExpiresOn = expiresOn,
             };
-            // Write + Create only — agent must not be able to Read other tenants' blobs,
-            // Delete anything, or List the container.
-            sasBuilder.SetPermissions(BlobSasPermissions.Write | BlobSasPermissions.Create);
+            // Create only — the agent does a single Put Blob of a brand-new name. No Write
+            // (would let the holder replace an existing blob of the same tenant), no Read,
+            // no Delete, no List.
+            sasBuilder.SetPermissions(UploadSasPermissions);
 
             if (UsesManagedIdentity)
             {
@@ -337,6 +371,26 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
                 throw new ArgumentException("filename must not contain null bytes", nameof(filename));
         }
 
+        /// <summary>
+        /// Binds an upload filename to the requesting session: it must be
+        /// <c>AgentDiagnostics-{sessionId}-{anything}.zip</c> (the shape the agent has always
+        /// produced, incl. the <c>-preprov</c>/<c>-server-requested</c> suffixes). Without this
+        /// an authenticated device could name any other session's package in its tenant.
+        /// Throws <see cref="ArgumentException"/> on rejection.
+        /// </summary>
+        internal static void EnsureFilenameBoundToSession(string filename, string sessionId)
+        {
+            var required = $"{PackageNamePrefix}{sessionId}-";
+            if (!filename.StartsWith(required, StringComparison.OrdinalIgnoreCase)
+                || filename.Length <= required.Length
+                || !filename.EndsWith(".zip", StringComparison.OrdinalIgnoreCase))
+            {
+                throw new ArgumentException(
+                    "filename must be of the form 'AgentDiagnostics-{sessionId}-{timestamp}.zip' for the requesting session",
+                    nameof(filename));
+            }
+        }
+
         /// <summary>
         /// Validates a stored blob path (<c>{tenantId}/{filename}</c>) on the read paths.
         /// Defends the download proxy against path-traversal even if a row was tampered with.
@@ -358,6 +412,22 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
         }
     }
 
+    /// <summary>
+    /// Thrown by <see cref="HostedDiagnosticsBlobService.GenerateUploadSasAsync"/> when the
+    /// requested blob name is already taken. Distinct from <see cref="ArgumentException"/>
+    /// (malformed input → 400) so the Function can answer 409.
+    /// </summary>
+    public sealed class HostedBlobAlreadyExistsException : InvalidOperationException
+    {
+        public HostedBlobAlreadyExistsException(string blobPath)
+            : base($"Hosted diagnostics blob already exists: {blobPath}")
+        {
+            BlobPath = blobPath;
+        }
+
+        public string BlobPath { get; }
+    }
+
     /// <summary>
     /// Return value of <see cref="HostedDiagnosticsBlobService.GenerateUploadSasAsync"/>.
     /// </summary>

src/Backend/AutopilotMonitor.Functions/Services/Diagnostics/SessionReportDiagnosticsArchiveCopier.cs

@@ -1,4 +1,5 @@
 using AutopilotMonitor.Functions.Functions.Diagnostics;
+using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Shared.Models;
 using Azure;
 using Azure.Storage.Blobs;
@@ -100,6 +101,16 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
             if (string.IsNullOrEmpty(sourceBlobName))
                 return new DiagnosticsArchiveCopyResult(false, Statuses.FailedNoDiagnostics, null);
 
+            // Destination is derived from request data (tenant/session ids). A non-flat name
+            // would let the SDK + System.Uri walk out of the session-reports container.
+            if (!BlobNameGuard.IsFlat(destinationBlobName))
+            {
+                _logger.LogWarning(
+                    "DiagnosticsArchiveCopier: rejecting non-flat destination blob name for tenant {TenantId}, session {SessionId}",
+                    tenantId, sessionId);
+                return new DiagnosticsArchiveCopyResult(false, Statuses.FailedInvalidBlobName, null);
+            }
+
             try
             {
                 var (destination, classifyErr) = DiagnosticsDownloadFunction.ClassifyBlobName(sourceBlobName, tenantId);
@@ -219,7 +230,7 @@ namespace AutopilotMonitor.Functions.Services.Diagnostics
         {
             var containerClient = _blobStorage.GetContainerClient(ReportsContainerName);
             await containerClient.CreateIfNotExistsAsync(cancellationToken: cancellationToken);
-            var blobClient = containerClient.GetBlobClient(destinationBlobName);
+            var blobClient = containerClient.GetBlobClient(BlobNameGuard.EnsureFlat(destinationBlobName, nameof(destinationBlobName)));
             await blobClient.UploadAsync(content, new BlobUploadOptions
             {
                 HttpHeaders = new BlobHttpHeaders { ContentType = "application/zip" }

src/Backend/AutopilotMonitor.Functions/Services/EmailTemplateService.cs

@@ -2,6 +2,7 @@ using AutopilotMonitor.Shared.DataAccess;
 using AutopilotMonitor.Shared.Models;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
+using System.Net;
 
 namespace AutopilotMonitor.Functions.Services;
 
@@ -73,10 +74,15 @@ public class EmailTemplateService : IEmailTemplateProvider
         ? EmailTemplates.GetPreviewApprovedHtml(DomainPlaceholder)
         : EmailTemplates.GetOffboardingFarewellHtml(DomainPlaceholder);
 
-    /// <summary>Substitutes the placeholder; an empty domain becomes "your organization".</summary>
+    /// <summary>
+    /// Substitutes the placeholder; an empty domain becomes "your organization". The value is
+    /// HTML-encoded at the point of substitution: the mail goes out under the product's signed
+    /// sender to a tenant-chosen recipient, so no writer of DomainName — current or future — may
+    /// ever be able to inject markup into it.
+    /// </summary>
     public static string Render(string rawHtml, string? domainName)
     {
-        var display = string.IsNullOrWhiteSpace(domainName) ? EmptyDomainLabel : domainName.Trim();
+        var display = string.IsNullOrWhiteSpace(domainName) ? EmptyDomainLabel : WebUtility.HtmlEncode(domainName.Trim());
         return rawHtml.Replace(DomainPlaceholder, display, StringComparison.Ordinal);
     }
 

src/Backend/AutopilotMonitor.Functions/Services/EmailTemplates.cs

@@ -1,3 +1,4 @@
+using System.Net;
 using AutopilotMonitor.Shared;
 
 namespace AutopilotMonitor.Functions.Services;
@@ -26,7 +27,7 @@ public static class EmailTemplates
     /// </summary>
     public static string GetOffboardingFarewellHtml(string domainName)
     {
-        var displayDomain = string.IsNullOrWhiteSpace(domainName) ? "your organization" : domainName;
+        var displayDomain = string.IsNullOrWhiteSpace(domainName) ? "your organization" : WebUtility.HtmlEncode(domainName);
 
         return $@"
 <!DOCTYPE html>
@@ -125,7 +126,7 @@ public static class EmailTemplates
     /// </summary>
     public static string GetPreviewApprovedHtml(string domainName)
     {
-        var displayDomain = string.IsNullOrWhiteSpace(domainName) ? "your organization" : domainName;
+        var displayDomain = string.IsNullOrWhiteSpace(domainName) ? "your organization" : WebUtility.HtmlEncode(domainName);
 
         return $@"
 <!DOCTYPE html>

src/Backend/AutopilotMonitor.Functions/Services/SessionReportService.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using Azure.Storage.Blobs.Models;
+using AutopilotMonitor.Functions.Security;
 using AutopilotMonitor.Functions.Services.Diagnostics;
 using AutopilotMonitor.Shared.DataAccess;
 using AutopilotMonitor.Shared.Models;
@@ -60,6 +61,11 @@ namespace AutopilotMonitor.Functions.Services
             SubmitSessionReportRequest request,
             string submittedBy)
         {
+            // Both identifiers shape blob names below; a non-GUID value could smuggle path
+            // separators / dot segments into the storage URI (cross-container write).
+            SecurityValidator.EnsureValidGuid(request.TenantId, nameof(request.TenantId));
+            SecurityValidator.EnsureValidGuid(request.SessionId, nameof(request.SessionId));
+
             var reportId = Guid.NewGuid().ToString("N")[..12];
             var timestamp = DateTime.UtcNow.ToString("yyyyMMdd_HHmmss");
             var blobName = $"{request.TenantId}_{request.SessionId}_diag_request_{timestamp}.zip";
@@ -203,7 +209,7 @@ namespace AutopilotMonitor.Functions.Services
             zipStream.Position = 0;
             var containerClient = _blobStorage.GetContainerClient(ContainerName);
             await containerClient.CreateIfNotExistsAsync();
-            var blobClient = containerClient.GetBlobClient(blobName);
+            var blobClient = containerClient.GetBlobClient(BlobNameGuard.EnsureFlat(blobName, nameof(blobName)));
             await blobClient.UploadAsync(zipStream, new BlobUploadOptions
             {
                 HttpHeaders = new BlobHttpHeaders { ContentType = "application/zip" }
@@ -245,6 +251,8 @@ namespace AutopilotMonitor.Functions.Services
             SubmitDiagFilesReportRequest request,
             string submittedBy)
         {
+            SecurityValidator.EnsureValidGuid(request.TenantId, nameof(request.TenantId));
+
             var reportId = Guid.NewGuid().ToString("N")[..12];
             var timestamp = DateTime.UtcNow.ToString("yyyyMMdd_HHmmss");
             var blobName = $"{request.TenantId}_diag_files_{timestamp}.zip";
@@ -292,7 +300,7 @@ namespace AutopilotMonitor.Functions.Services
             zipStream.Position = 0;
             var containerClient = _blobStorage.GetContainerClient(ContainerName);
             await containerClient.CreateIfNotExistsAsync();
-            var blobClient = containerClient.GetBlobClient(blobName);
+            var blobClient = containerClient.GetBlobClient(BlobNameGuard.EnsureFlat(blobName, nameof(blobName)));
             await blobClient.UploadAsync(zipStream, new BlobUploadOptions
             {
                 HttpHeaders = new BlobHttpHeaders { ContentType = "application/zip" }

src/Shared/AutopilotMonitor.Shared/Models/Config/TenantConfiguration.cs

@@ -1008,25 +1008,32 @@ namespace AutopilotMonitor.Shared.Models
         }
 
         /// <summary>
-        /// Gets manufacturer whitelist as array
+        /// Gets manufacturer whitelist as array (empty/whitespace = allow all)
         /// </summary>
-        public string[] GetManufacturerWhitelist()
-        {
-            if (string.IsNullOrEmpty(ManufacturerWhitelist))
-                return new[] { "*" };
-
-            return ManufacturerWhitelist.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
-        }
+        public string[] GetManufacturerWhitelist() => ParseWhitelist(ManufacturerWhitelist);
 
         /// <summary>
-        /// Gets model whitelist as array
+        /// Gets model whitelist as array (empty/whitespace = allow all)
         /// </summary>
-        public string[] GetModelWhitelist()
+        public string[] GetModelWhitelist() => ParseWhitelist(ModelWhitelist);
+
+        /// <summary>
+        /// Splits a stored hardware whitelist CSV into individual match patterns: trimmed, empty
+        /// entries dropped. The CSV is the ONLY storage format, so a ',' can never be part of a
+        /// pattern — writers (web editor, <c>TenantConfigValidation</c>) must guarantee each
+        /// intended entry lands as exactly one CSV item.
+        /// </summary>
+        public static string[] ParseWhitelist(string? csv)
         {
-            if (string.IsNullOrEmpty(ModelWhitelist))
+            if (string.IsNullOrWhiteSpace(csv))
                 return new[] { "*" };
 
-            return ModelWhitelist.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
+            var entries = csv!.Split(',')
+                .Select(e => e.Trim())
+                .Where(e => e.Length > 0)
+                .ToArray();
+
+            return entries.Length == 0 ? new[] { "*" } : entries;
         }
 
         /// <summary>

src/Web/autopilot-monitor-web/app/settings/components/HardwareWhitelistSection.tsx

@@ -3,6 +3,7 @@
 import { useState } from "react";
 import SaveResetBar from "./SaveResetBar";
 import ReadOnlyFieldset from "./ReadOnlyFieldset";
+import { joinList, parseList } from "../lib/hardwareWhitelist";
 
 interface HardwareWhitelistSectionProps {
   manufacturerWhitelist: string;
@@ -16,14 +17,6 @@ interface HardwareWhitelistSectionProps {
   readOnly?: boolean;
 }
 
-function parseList(csv: string): string[] {
-  return csv.split(",").map((s) => s.trim()).filter(Boolean);
-}
-
-function joinList(items: string[]): string {
-  return items.join(",");
-}
-
 function WhitelistEditor({
   label,
   description,
@@ -38,14 +31,17 @@ function WhitelistEditor({
   setItems: (items: string[]) => void;
 }) {
   const [newItem, setNewItem] = useState("");
-  const trimmed = newItem.trim();
-  const isDuplicate =
-    trimmed !== "" &&
-    items.some((a) => a.toLowerCase() === trimmed.toLowerCase());
+  // Admin-typed input is a LIST: "Dell*, *" adds two patterns (the placeholder invites
+  // exactly that). Only the insights buttons neutralize ',' — their values are untrusted.
+  const existing = new Set(items.map((a) => a.toLowerCase()));
+  const typed = parseList(newItem);
+  const fresh = typed.filter((t, i) =>
+    !existing.has(t.toLowerCase()) && typed.findIndex((u) => u.toLowerCase() === t.toLowerCase()) === i);
+  const isDuplicate = typed.length > 0 && fresh.length === 0;
 
   const addItem = () => {
-    if (!trimmed || isDuplicate) return;
-    setItems([...items, trimmed]);
+    if (fresh.length === 0) return;
+    setItems([...items, ...fresh]);
     setNewItem("");
   };
 
@@ -110,7 +106,7 @@ function WhitelistEditor({
         />
         <button
           onClick={addItem}
-          disabled={!trimmed || isDuplicate}
+          disabled={fresh.length === 0}
           className="px-4 py-1.5 bg-green-600 text-white rounded-lg text-sm font-medium hover:bg-green-700 disabled:opacity-50 disabled:cursor-not-allowed transition-colors whitespace-nowrap"
         >
           Add

src/Web/autopilot-monitor-web/app/settings/lib/__tests__/hardwareWhitelist.test.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from "vitest";
+import { addWhitelistEntry, parseList, toWhitelistEntry } from "../hardwareWhitelist";
+
+describe("hardware whitelist CSV helpers", () => {
+  it("adds a plain value as one entry", () => {
+    expect(addWhitelistEntry("Dell*,HP*", "Lenovo")).toBe("Dell*,HP*,Lenovo");
+  });
+
+  it("never lets a delimiter-bearing value expand into extra patterns", () => {
+    // Attacker-controlled distress-signal string: would become [..., "Dell Inc.", "*"] verbatim.
+    const csv = addWhitelistEntry("Dell*", "Dell Inc.,*");
+    expect(parseList(csv)).toEqual(["Dell*", "Dell Inc.?*"]);
+    expect(parseList(csv)).not.toContain("*");
+  });
+
+  it("neutralizes a trailing comma instead of creating an empty/stray entry", () => {
+    expect(parseList(addWhitelistEntry("Dell*", "Dell Inc.,"))).toEqual(["Dell*", "Dell Inc.?"]);
+  });
+
+  it("ignores empty and duplicate values", () => {
+    expect(addWhitelistEntry("Dell*", "  ")).toBe("Dell*");
+    // A lone delimiter becomes the single-character pattern "?" — one entry, never a split.
+    expect(parseList(addWhitelistEntry("Dell*", ","))).toEqual(["Dell*", "?"]);
+    expect(addWhitelistEntry("Dell*", "dell*")).toBe("Dell*");
+  });
+
+  it("toWhitelistEntry trims and replaces every comma", () => {
+    expect(toWhitelistEntry("  a,b,,c ")).toBe("a?b??c");
+  });
+});

src/Web/autopilot-monitor-web/app/settings/lib/hardwareWhitelist.ts

@@ -0,0 +1,37 @@
+/**
+ * Hardware whitelist CSV helpers.
+ *
+ * The tenant whitelist is persisted as ONE comma-separated string and split on ',' at
+ * enforcement time (TenantConfiguration.GetManufacturerWhitelist). A comma inside a single
+ * entry therefore changes the LIST STRUCTURE: "Dell Inc.,*" appended as one "manufacturer"
+ * becomes two patterns, the second being the allow-all wildcard. Manufacturer/model strings
+ * shown in the rejection insights come from UNAUTHENTICATED distress signals, so every value
+ * that enters the list must round-trip as exactly one pattern.
+ */
+
+export function parseList(csv: string): string[] {
+  return csv.split(",").map((s) => s.trim()).filter(Boolean);
+}
+
+export function joinList(items: string[]): string {
+  return items.join(",");
+}
+
+/**
+ * Normalizes a value so it is stored as exactly one whitelist pattern. The delimiter is
+ * replaced by the single-character wildcard '?', which still matches the original string
+ * literally (and nothing structurally different) instead of splitting the list.
+ * Returns "" when nothing usable remains.
+ */
+export function toWhitelistEntry(value: string): string {
+  return value.replace(/,/g, "?").trim();
+}
+
+/** Appends `value` as one pattern unless an equal (case-insensitive) entry already exists. */
+export function addWhitelistEntry(csv: string, value: string): string {
+  const entry = toWhitelistEntry(value);
+  if (!entry) return csv;
+  const items = parseList(csv);
+  if (items.some((i) => i.toLowerCase() === entry.toLowerCase())) return csv;
+  return joinList([...items, entry]);
+}

src/Web/autopilot-monitor-web/app/settings/tenant/sections/SectionHardwareWhitelist.tsx

@@ -7,14 +7,7 @@ import { TenantNotifications } from "../../TenantNotifications";
 import HardwareWhitelistSection from "../../components/HardwareWhitelistSection";
 import HardwareRejectionInsights from "../../components/HardwareRejectionInsights";
 import TpmIncompatibleDevicesInsights from "../../components/TpmIncompatibleDevicesInsights";
-
-function parseList(csv: string): string[] {
-  return csv.split(",").map((s) => s.trim()).filter(Boolean);
-}
-
-function joinList(items: string[]): string {
-  return items.join(",");
-}
+import { addWhitelistEntry } from "../../lib/hardwareWhitelist";
 
 export function SectionHardwareWhitelist() {
   const { getAccessToken } = useAuth();
@@ -30,18 +23,14 @@ export function SectionHardwareWhitelist() {
 
   const hasWebhook = notificationChannels.some((c) => c.enabled && (c.url ?? "").length > 0);
 
+  // Values come from UNAUTHENTICATED distress signals — addWhitelistEntry guarantees each
+  // click adds exactly one pattern (a ',' inside the value cannot split the list).
   const handleAddManufacturer = useCallback((value: string) => {
-    const items = parseList(manufacturerWhitelist);
-    if (!items.some((i) => i.toLowerCase() === value.toLowerCase())) {
-      setManufacturerWhitelist(joinList([...items, value]));
-    }
+    setManufacturerWhitelist(addWhitelistEntry(manufacturerWhitelist, value));
   }, [manufacturerWhitelist, setManufacturerWhitelist]);
 
   const handleAddModel = useCallback((value: string) => {
-    const items = parseList(modelWhitelist);
-    if (!items.some((i) => i.toLowerCase() === value.toLowerCase())) {
-      setModelWhitelist(joinList([...items, value]));
-    }
+    setModelWhitelist(addWhitelistEntry(modelWhitelist, value));
   }, [modelWhitelist, setModelWhitelist]);
 
   return (