I'm using MediaWiki 1.26 and CentralAuth on a wiki farm, and want to upgrade to 1.27, but when logging in (on the new 1.27 wiki - all extensions are 1.27 too), CentralAuth (Special:CentralLogin/complete?token=<token>) gives this error:
Central user log in
No active login attempt is in progress for your session.
The error seems to come from $attempt = $request->getSessionData( $skey ); if ( !isset( $attempt['secret'] ) ), $attempt is NULL here.
Why can $attempt be null?