When trying to communicate between an iframe and the main window using Window.postMessage() I get the error:
Blocked a frame with origin "null" from accessing a frame with origin "null"
This only happens from the iframe to the main window, when communicating the other way around it works fine.
Both files are run locally. The error only happens after adding the plugin cordova-plugin-wkwebview-engine. When using UIWebView the error does not happen.
The weird thing is that this error is shown exactly 11 times, but the message goes through anyway. See this screenshot taken from Safari while using the simulator: http://i.imgur.com/JJkIEy5.jpg You can see the MessageEvent happening at the end.
I have added sandbox="allow-same-origin allow-scripts allow-popups allow-forms" to the iframe tag but it didn't fix it.
This is the code that listens to the message:
window.addEventListener("message", eventHandler, false);
And this is the code that emits the message from the iframe: