We embedded Google OAuth button inside iframe. When user loads a page with this iframe, clicks Google button from that iframe, window.gapi.auth2.getAuthInstance().signIn fires and new window appears. User enters email, password and submits form. Window closes but there is no callback to this function.
It only reproduces when main window domain is different to iframe domain!
You can try here - https://sparklejobs.com/localhost-universal/
Main window domain - sparklejobs.com Iframe window with Google button - staging-web.good.co