The PostNuke team is advising users who may have installed the compromised files to reinstall the code, and immediately change their database details, including username, password and the name of the database if possible.
PostNuke is a development fork of the PHPNuke content management system. Both programs are open source projects using PHP and a MySQL database that are widely used but have a history of security issues. The attacker in Sunday night’s attack used a security hole in pafiledb, a download management app that is not part of the official PostNuke software, but was used to maintain the PostNuke site. The flaw in the .zip archive was detected by a user and posted to the PostNuke forum Monday evening.