Does anyone know of a way to use ItchIO's OAuth for a Unity3D WebGL game hosted on ItchIO?

I'm am not sure what to try next as the game itself is loaded in an IFrame and unable to read the access_token from the parent pages URI after a user has agreed and been redirected back to the game due to cross-origin issues between the Iframe and parent page.

Error: DOMException: Permission denied to access property "hash" on cross-origin object

    var queryString = window.parent.location.hash.slice(1);//Error Here     
    var params = new URLSearchParams(queryString);     
    var accessToken = params.get("access_token");      
    console.log(accessToken); 

Note: window.location has the games Iframe URI without the access_token