diff --git a/src/components/Header/HeaderLogo.tsx b/src/components/Header/HeaderLogo.tsx
index 7825014c4..509602a8c 100644
--- a/src/components/Header/HeaderLogo.tsx
+++ b/src/components/Header/HeaderLogo.tsx
@@ -102,11 +102,11 @@ function LogoFallback(props: HeaderLogoProps) {
                           }
                         : {
                               light: {
-                                  src: absoluteHref('~gitbook/icon?size=medium&theme=light'),
+                                  src: absoluteHref('~gitbook/icon?size=medium&theme=light', true),
                                   size: { width: 256, height: 256 },
                               },
                               dark: {
-                                  src: absoluteHref('~gitbook/icon?size=medium&theme=dark'),
+                                  src: absoluteHref('~gitbook/icon?size=medium&theme=dark', true),
                                   size: { width: 256, height: 256 },
                               },
                           }
diff --git a/src/lib/images.ts b/src/lib/images.ts
index f1529dd8d..a3e1b2e77 100644
--- a/src/lib/images.ts
+++ b/src/lib/images.ts
@@ -122,6 +122,15 @@ export async function resizeImage(
 ): Promise<Response> {
     const { signal, ...resizeOptions } = options;
 
+    const parsed = new URL(input);
+    if (parsed.protocol === 'data:') {
+        throw new Error('Cannot resize data: URLs');
+    }
+
+    if (parsed.hostname === 'localhost') {
+        throw new Error('Cannot resize localhost URLs');
+    }
+
     // Since Cloudflare Images options on fetch are not supported on Cloudflare Pages,
     // we need to use the Cloudflare Image Resize API directly.
     if (process.env.GITBOOK_IMAGE_RESIZE_URL) {