diff --git a/.changeset/red-bats-chew.md b/.changeset/red-bats-chew.md
new file mode 100644
index 000000000..33c9ccefd
--- /dev/null
+++ b/.changeset/red-bats-chew.md
@@ -0,0 +1,5 @@
+---
+'@gitbook/react-contentkit': patch
+---
+
+Fix rendering of webframe with SSR causing wrong communication between frame and renderer
diff --git a/.changeset/shy-buttons-relate.md b/.changeset/shy-buttons-relate.md
new file mode 100644
index 000000000..4f1c7585f
--- /dev/null
+++ b/.changeset/shy-buttons-relate.md
@@ -0,0 +1,5 @@
+---
+'gitbook': patch
+---
+
+Add optional env `GITBOOK_INTEGRATIONS_HOST` to configure the host serving the integrations
diff --git a/packages/gitbook/src/components/DocumentView/Integration/IntegrationBlock.tsx b/packages/gitbook/src/components/DocumentView/Integration/IntegrationBlock.tsx
index f5d98f712..5278203ef 100644
--- a/packages/gitbook/src/components/DocumentView/Integration/IntegrationBlock.tsx
+++ b/packages/gitbook/src/components/DocumentView/Integration/IntegrationBlock.tsx
@@ -3,6 +3,7 @@ import { Icon } from '@gitbook/icons';
 import { ContentKit, ContentKitOutput, ContentKitServerContext } from '@gitbook/react-contentkit';
 
 import { ignoreAPIError, renderIntegrationUi } from '@/lib/api';
+import { INTEGRATIONS_HOST } from '@/lib/csp';
 import { parseMarkdown } from '@/lib/markdown';
 import { tcls } from '@/lib/tailwind';
 
@@ -69,7 +70,7 @@ export async function IntegrationBlock(props: BlockProps<DocumentBlockIntegratio
     return (
         <div className={tcls(style)}>
             <ContentKit
-                security={{ firstPartyDomains: ['integrations.gitbook.com'] }}
+                security={{ firstPartyDomains: [INTEGRATIONS_HOST] }}
                 initialInput={initialInput}
                 initialOutput={initialOutput}
                 render={async (request) => {
diff --git a/packages/gitbook/src/lib/csp.ts b/packages/gitbook/src/lib/csp.ts
index 465a197fe..e883c8f58 100644
--- a/packages/gitbook/src/lib/csp.ts
+++ b/packages/gitbook/src/lib/csp.ts
@@ -25,6 +25,12 @@ export function createContentSecurityPolicyNonce(): string {
     return nonce;
 }
 
+/**
+ * Hostname serving the integrations.
+ */
+export const INTEGRATIONS_HOST =
+    process.env.GITBOOK_INTEGRATIONS_HOST ?? 'integrations.gitbook.com';
+
 /**
  * Generate a Content Security Policy header for a space.
  */
@@ -39,10 +45,10 @@ export function getContentSecurityPolicy(scripts: SpaceIntegrationScript[], nonc
     // Since I can't get the nonce to work for inline styles, we need to allow unsafe-inline
     const defaultCSP = `
         default-src 'self' ${assetsDomain};
-        script-src 'self' 'nonce-${nonce}' 'strict-dynamic' 'unsafe-inline' 'unsafe-eval' ${assetsDomain} https://integrations.gitbook.com https://cdn.iframe.ly;
+        script-src 'self' 'nonce-${nonce}' 'strict-dynamic' 'unsafe-inline' 'unsafe-eval' ${assetsDomain} https://${INTEGRATIONS_HOST} https://cdn.iframe.ly;
         style-src 'self' ${assetsDomain} fonts.googleapis.com 'unsafe-inline';
         img-src * 'self' blob: data: files.gitbook.com ${assetsDomain} ${iconsAssetsSrc};
-        connect-src * 'self' integrations.gitbook.com app.gitbook.com api.gitbook.com srv.buysellads.com ${assetsDomain} ${iconsAssetsSrc};
+        connect-src * 'self' ${INTEGRATIONS_HOST} app.gitbook.com api.gitbook.com srv.buysellads.com ${assetsDomain} ${iconsAssetsSrc};
         font-src 'self' fonts.gstatic.com ${assetsDomain};
         frame-src *;
         object-src 'none';
diff --git a/packages/react-contentkit/src/ElementWebframe.tsx b/packages/react-contentkit/src/ElementWebframe.tsx
index ec7f97477..866c8e8f5 100644
--- a/packages/react-contentkit/src/ElementWebframe.tsx
+++ b/packages/react-contentkit/src/ElementWebframe.tsx
@@ -10,6 +10,7 @@ import { resolveDynamicBinding } from './dynamic';
 export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWebFrame>) {
     const { element } = props;
 
+    const [mounted, setMounted] = React.useState(false);
     const renderer = useContentKitClientContext();
     const iframeRef = React.useRef<HTMLIFrameElement>(null);
     const [size, setSize] = React.useState<{
@@ -23,10 +24,6 @@ export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWe
 
     const sendMessage = React.useCallback(
         (message: object) => {
-            if (!iframeRef.current) {
-                return;
-            }
-
             const target = new URL(element.source.url);
 
             // For security reasons, only iframe from our integrations domains are allowed
@@ -36,6 +33,10 @@ export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWe
             }
 
             if (readyRef.current) {
+                if (!iframeRef.current) {
+                    return;
+                }
+
                 iframeRef.current.contentWindow!.postMessage(
                     message,
                     `${target.protocol}//${target.host}`,
@@ -61,7 +62,7 @@ export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWe
 
             // For security reasons, only iframe from our integrations domains are allowed
             // to send and receive messages
-            if (!renderer.security.firstPartyDomains.includes(origin.host) && 0) {
+            if (!renderer.security.firstPartyDomains.includes(origin.host)) {
                 return;
             }
 
@@ -117,6 +118,11 @@ export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWe
         };
 
         window.addEventListener('message', callback);
+
+        // We only render the iframe once we have added the event listener
+        // otherwise during SSR, we'll miss messages
+        setMounted(true);
+
         return () => {
             window.removeEventListener('message', callback);
         };
@@ -142,26 +148,29 @@ export function ElementWebframe(props: ContentKitClientElementProps<ContentKitWe
         <div
             className={`contentkit-webframe`}
             style={{
-                aspectRatio: element.aspectRatio,
-                ...size,
+                aspectRatio: size.aspectRatio || element.aspectRatio || undefined,
+                maxWidth: size.maxWidth || undefined,
+                maxHeight: size.maxHeight || undefined,
             }}
         >
-            <iframe
-                ref={iframeRef}
-                src={element.source.url}
-                allowFullScreen
-                allow="clipboard-write"
-                style={{
-                    position: 'absolute',
-                    top: 0,
-                    left: 0,
-                    bottom: 0,
-                    right: 0,
-                    width: '100%',
-                    height: '100%',
-                    border: 'none',
-                }}
-            />
+            {mounted ? (
+                <iframe
+                    ref={iframeRef}
+                    src={element.source.url}
+                    allowFullScreen
+                    allow="clipboard-write"
+                    style={{
+                        position: 'absolute',
+                        top: 0,
+                        left: 0,
+                        bottom: 0,
+                        right: 0,
+                        width: '100%',
+                        height: '100%',
+                        border: 'none',
+                    }}
+                />
+            ) : null}
         </div>
     );
 }