diff --git a/packages/extension/src/entrypoints/content.ts b/packages/extension/src/entrypoints/content.ts
index 1bcfc8a..e7913bb 100644
--- a/packages/extension/src/entrypoints/content.ts
+++ b/packages/extension/src/entrypoints/content.ts
@@ -46,6 +46,8 @@ async function exposeAgentToPage() {
 	let multiPageAgent: InstanceType<typeof MultiPageAgent> | null = null
 
 	window.addEventListener('message', async (e) => {
+		if (e.source !== window) return
+
 		const data = e.data
 		if (typeof data !== 'object' || data === null) return
 		if (data.channel !== 'PAGE_AGENT_EXT_REQUEST') return
diff --git a/packages/extension/src/entrypoints/main-world.ts b/packages/extension/src/entrypoints/main-world.ts
index b401beb..61973e9 100644
--- a/packages/extension/src/entrypoints/main-world.ts
+++ b/packages/extension/src/entrypoints/main-world.ts
@@ -45,6 +45,8 @@ export default defineUnlistedScript(() => {
 
 		const promise = new Promise<ExecutionResult>((resolve, reject) => {
 			function handleMessage(e: MessageEvent) {
+				if (e.source !== window) return
+
 				const data = e.data
 				if (typeof data !== 'object' || data === null) return
 				if (data.channel !== 'PAGE_AGENT_EXT_RESPONSE') return