Seems like SAU/BOOSTCRUSING/FORDFORUMS and PERFORMANCEFORUMS have been hit by the same thing. Other people report using exclusive email addresses for those forums too.
https://www.google.com.au/search?biw....0.Q_lISWyeyy0
4x Australian+Motoring related forums.
Hmmm.
Inside job maybe unless they are also vBulletin (edit: 2x Invision + 2x vBulletin)