From e08e46190145e27119a88ac39cb2cea904b1c39b Mon Sep 17 00:00:00 2001
From: Matt Hillsdon <matt.hillsdon@microbit.org>
Date: Tue, 10 Sep 2024 13:43:46 +0100
Subject: [PATCH] Tweak origin check to respect the configured URL

---
 src/vanilla/makecode-frame-driver.ts | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/vanilla/makecode-frame-driver.ts b/src/vanilla/makecode-frame-driver.ts
index 30cddf7..ba317eb 100644
--- a/src/vanilla/makecode-frame-driver.ts
+++ b/src/vanilla/makecode-frame-driver.ts
@@ -166,8 +166,22 @@ export class MakeCodeFrameDriver {
     }
   >();
 
+  private _expectedOrigin: string | undefined;
+  private expectedOrigin = () => {
+    if (this._expectedOrigin) {
+      return this._expectedOrigin;
+    }
+    const src = this.iframe()?.src;
+    if (src) {
+      this._expectedOrigin = new URL(src).origin;
+      return this._expectedOrigin;
+    }
+    return undefined;
+  };
+
   private listener = (event: MessageEvent) => {
-    if (event.origin !== 'https://makecode.microbit.org') {
+    const expectedOrigin = this.expectedOrigin();
+    if (!expectedOrigin || event.origin !== expectedOrigin) {
       return;
     }
     const { data } = event;