fix: stop window.open from hanging when prevented (#29851)

lib/browser/guest-window-proxy.ts

@@ -76,6 +76,7 @@ ipcMainInternal.on(
     const referrer: Electron.Referrer = { url: '', policy: 'strict-origin-when-cross-origin' };
     const browserWindowOptions = event.sender._callWindowOpenHandler(event, { url, frameName, features, disposition: 'new-window', referrer });
     if (event.defaultPrevented) {
+      event.returnValue = null;
       return;
     }
     const guest = openGuestWindow({

spec-main/guest-window-manager-spec.ts

@@ -263,6 +263,12 @@ describe('webContents.setWindowOpenHandler', () => {
 
         browserWindow.webContents.executeJavaScript("window.open('about:blank', '', 'show=no') && true");
       });
+
+      it('does not hang parent window when denying window.open', async () => {
+        browserWindow.webContents.setWindowOpenHandler(() => ({ action: 'deny' }));
+        browserWindow.webContents.executeJavaScript("window.open('https://127.0.0.1')");
+        expect(await browserWindow.webContents.executeJavaScript('42')).to.equal(42);
+      });
     });
   }
 });