When using multiple sites as a wiki family it appears that GoogleLogin does not use the correct URL for each site. This returns the wrong site (not the site the request was initiated from):

SpecialPage::getTitleFor( 'GoogleLoginReturn' )->getFullURL( '', false, PROTO_CURRENT )

as well as this:

SpecialPage::getTitleFor( 'Userlogin' )->getLocalURL();

And I think somewhere else that I haven't found in the extension. The wiki is working otherwise, so I'm not sure why this would return the wrong result?