Catalin Cimpanu reports:
Administrators of the vBulletin forums have started a site-wide password reset operation after an unknown attacker has gained access to one of their servers.
Last Thursday the vBulleting.org (sic) and vBulleting.com (sic) domains went offline for maintenance and remained so until Friday afternoon. As soon as the forums came back online, all users were forced to reset their passwords in order to access their accounts.
The combination of this non-scheduled maintenance and the forced password reset is a typical sign of a data breach. The hacking incident was confirmed hours later on Friday by Paul M., Lead Developer for vBulletin.org & vBulletin.com.
Read more on Softpedia. This seems unrelated to the breach this site reported in November, 2015.