title: Firebase RealTime Database CORS Issue
body: <p>I am using Firebase Realtime Database on my web site, all works fine, but, when I want to do auth with custom json token I am getting a CORS issue like this: "Request from another blocked source: the same source policy prevents reading the remote resource in <a href="https://www.googleapis.com/identitytoolkit/v3/relyingparty/verifyCustomToken?key=" rel="nofollow noreferrer">https://www.googleapis.com/identitytoolkit/v3/relyingparty/verifyCustomToken?key=</a>$somekey".</p>
  
  <p>Thanks</p>