At first I though you wouldn't be able to stay "in the middle" because you'd have to redirect to the typed address. You can't AJAX it in, because of CORS. But

At first I though you wouldn't be able to stay "in the middle" because you'd have to redirect to the typed address. You can't AJAX it in, because of CORS. But you could go to your own host and have your server sit in the middle. The user wouldn't be logged in, since cookies wouldn't be sent. But maybe they would login through your proxy.