diff --git a/components/providers/embedded-bridge-provider.tsx b/components/providers/embedded-bridge-provider.tsx
index 3cb6edc4..6a1d4060 100644
--- a/components/providers/embedded-bridge-provider.tsx
+++ b/components/providers/embedded-bridge-provider.tsx
@@ -12,6 +12,14 @@ export function EmbeddedBridgeProvider({ children }: { children: React.ReactNode
 
   useEffect(() => {
     if (!embeddedMode || !isEmbedded()) return;
+    // Refuse to attach the listener without a pinned parent origin —
+    // otherwise any cross-origin frame could forge sso:trigger-logout.
+    if (!parentOrigin) {
+      console.error(
+        "[embedded-bridge] embeddedMode is enabled but parentOrigin is not configured; refusing to attach message listener",
+      );
+      return;
+    }
 
     const unsubscribe = listenFromParent((msg) => {
       switch (msg.type) {
@@ -26,7 +34,7 @@ export function EmbeddedBridgeProvider({ children }: { children: React.ReactNode
           logout();
           break;
       }
-    }, parentOrigin || undefined);
+    }, parentOrigin);
 
     return unsubscribe;
   }, [embeddedMode, parentOrigin, logout]);
diff --git a/lib/iframe-bridge.ts b/lib/iframe-bridge.ts
index fbe28070..431bf3dc 100644
--- a/lib/iframe-bridge.ts
+++ b/lib/iframe-bridge.ts
@@ -1,6 +1,17 @@
+function normalizeOrigin(value: string): string | null {
+  if (!value) return null;
+  try {
+    const u = new URL(value);
+    if (u.protocol !== 'https:' && u.protocol !== 'http:') return null;
+    return u.origin;
+  } catch {
+    return null;
+  }
+}
+
 const PARENT_ORIGIN = typeof window !== 'undefined'
-  ? (document.querySelector('meta[name="parent-origin"]')?.getAttribute('content') || '')
-  : '';
+  ? normalizeOrigin(document.querySelector('meta[name="parent-origin"]')?.getAttribute('content') || '')
+  : null;
 
 export function isEmbedded(): boolean {
   try {
@@ -12,10 +23,13 @@ export function isEmbedded(): boolean {
 
 export function notifyParent(type: string, payload: Record<string, unknown> = {}) {
   if (!isEmbedded()) return;
+  // Refuse to broadcast when the parent origin is unknown. A wildcard
+  // targetOrigin would leak the payload (e.g. username) to any frame
+  // the parent has open.
+  if (!PARENT_ORIGIN) return;
 
-  const targetOrigin = PARENT_ORIGIN || '*';
   try {
-    window.parent.postMessage({ source: 'bulwark', type, ...payload }, targetOrigin);
+    window.parent.postMessage({ source: 'bulwark', type, ...payload }, PARENT_ORIGIN);
   } catch {
     // Cross-origin postMessage may fail in restricted contexts
   }
@@ -23,13 +37,22 @@ export function notifyParent(type: string, payload: Record<string, unknown> = {}
 
 export function listenFromParent(
   handler: (msg: { type: string; [k: string]: unknown }) => void,
-  allowedOrigin?: string,
+  allowedOrigin: string,
 ): () => void {
-  const listener = (event: MessageEvent) => {
-    // Validate origin if configured
-    if (allowedOrigin && event.origin !== allowedOrigin) return;
+  // Reject installation entirely when the caller cannot pin an origin.
+  // Without this gate any cross-origin frame could forge
+  // { source: 'portal', type: 'sso:trigger-logout' } and ride the session.
+  const normalized = normalizeOrigin(allowedOrigin);
+  if (!normalized) {
+    if (typeof console !== 'undefined') {
+      console.error('[iframe-bridge] listenFromParent requires a valid http(s) allowedOrigin; listener not installed');
+    }
+    return () => {};
+  }
 
-    // Only accept messages from the portal
+  const listener = (event: MessageEvent) => {
+    if (event.origin !== normalized) return;
+    if (event.source !== window.parent) return;
     if (!event.data || event.data.source !== 'portal') return;
 
     handler(event.data);