The online bulletin board phpBB (php Bulletin Board) was taken offline on Sunday, following a security breach that allowed access to user account details. phpBB is an open-source software package used to run discussion forums on web sites. The breach was caused when the attacker gained access through an unpatched security bug in PHPlist, a third-party open source email application, used for managing newsletters. The attacker had access for more than two weeks before the breach was discovered.
Read more on Heise Online. The Register also has coverage.
Thanks to Brian Honan for the links.