Fix sandbox tests

Author: Ives van Hoorne

packages/app/scripts/start.js

@@ -186,7 +186,12 @@ function addMiddleware(devServer, index) {
     })
   );
   if (process.env.LOCAL_SERVER) {
-    devServer.use(cors());
+    devServer.use(
+      cors({
+        origin: ['http://localhost:3000', 'http://localhost:3002'],
+        credentials: true,
+      })
+    );
     devServer.use(
       '/api',
       proxy({