So I am ruing a bridge plugin that hooks Xenforo forum into Wordpress, with single sign-on (User authentication is entirely handled by Xenforo, and all WP login/registrations etc are redirected to matching Xenforo links).
However in wp-admin, upon cookie expiration a popup iframe appears with a login form, though with this bridge it literally loads the entire Xenforo's login page.
Because I'm trying to modify the display of this page w/o using exteal changes to Xenforo, I suppose the only way would be to inject custom CSS into the iframe popup and use display:none on all the Xenforo elements I don't want. Basically I don't want an entire web page loading in the popup, but just a simple login form like the default WP form.
I've scaed dozens of files and can't locate the WP file that produces this popup window, any help?
Could accomplishing something like this be included in a plugin file or adding filters, w/o making changes to WP core files?