If I'd granted extended permission, even though after I logged out of facebook and WordPress, cleared cache, but I noticed I got logged in again after restarted the browser Chrome.

Also, at the login page of wp-admin, I saw a huge ugly icon said register with Facebook, but when clicked on it, it just redirected me back to the same wp-admin page, but without the ugly oversized Facebook logo. You know what I meant if you take a look at the attachment below.