Just before UG hackers claimed to of hacked the mybb servers, it was fairly clear that this had happened but now we can 100% confirm this with the following message from the Mybb administration. The message was posted on a amazon storage server and linked to via twitter.

Dear MyBB users,

Last night our domain name and hosting accounts were compromised by hackers. Users of MyBB should not be concerned about their own installations. There is nothing to indicate the MyBB software itself contributed to the hacking in any way. We hope to restore access to all services in the next 12 - 24 hours. At this stage we don't believe our database was compromised, however we recommend users stay vigilant to unauthorized access of their accounts.

Download MyBB 1.6.8 (latest release)

We recommend you stay informed by following MyBB on facebook and twitter. Regards, The MyBB Group.