The WordPress.org development team has released version 3.1.3 of its open source blogging and publishing platform; this is a maintenance and security update to WordPress 3.1 released in late February. According to the developers, the stable update features security hardening and taxonomy query hardening, and prevents the sniffing out of user names of non-authors by using canonical redirects.
WordPress 3.1.3 also introduces clickjacking protection in modern browsers on admin and login pages. In the event of an import not completing, the old import files will be cleaned up automatically. Other changes include media security fixes and improved file upload security.
Continued : http://www.h-online.com/security/news/item/WordPress-3-1-3-and-3-2-Beta-2-released-1250772.html
Also: WordPress 3.1.3 Contains Security Fixes and Clickjacking Protection