Well, I'm trying to run an iframe or window.open in my subdomain page to access the domain page for Google Login permission purposes. But i'm getting the cross origin error.

My principal page is: http://subdomain.lvh.me:3000

And when I click on the button, a new pages open or the iframe opens (does not make difference) with the URL: http://lvh.me:3000

But in this way I can't access iframe.contentWindow.document to get the iframe content value from the principal page. That is the situation: Image error

And, when I try to send by window.postMessage, this is the error: postMessage error

Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('http://subdomin.lvh.me:3001') does not match the recipient window's origin ('http://lvh.me:3001').