WordPress 3.9.2 is now available as a security release for all previous versions. We strongly encourage you to update your sites immediately or your site may be vulnerable to DOS attacks.
According to WordPress, this release fixes a possible denial of service issue in PHP’s XML processing, reported by Nir Goldshlager of the Salesforce.com Product Security Team. It was fixed by Michael Adams and Andrew Nacin of the WordPress security team and David Rothstein of the Drupal security team. This is the first time the two projects have coordinated joint security releases.