Hackers are believed to have compromised the accounts of millions of users operating or developing the Drupal open-source content management system (CMS).
The Drupal Association says an individual or group has gained unauthorised access to the accounts on its Drupal.org and groups.drupal.org sites.
Information exposed includes user names, email addresses, country information and hashed passwords.
Websites running the Drupal CMS, however, are not believed to be affected, Drupal Association executive director Holly Ross said.
Ross, though, advised users to reset passwords on all other sites where they'd used similar passwords to those on Drupal.org and groups.drupal.org.
The exec also pointed out that the hack wasn't the result of a vulnerability in the Drupal software itself, but rather that hackers had attacked via a flaw in third-party software installed on the Drupal.org server.
Prominent users of Drupal include the US White House, MTV, Sony, Warner Music, the BBC and The Economist, while Drupal serves as a core platform for more than 10,00 modules. It competes against WordPress, Blogger and Joomla.
Drupal has now reset the passwords on accounts and asked users to pick a new password next time they log in. Ross warned Drupal users to look out for suspicious emails asking for personal information and to be on the look out for spam.
“Also, beware of emails that threaten to close your account if you do not take the 'immediate action' of providing personal information,” Ross wrote. ®