- Various security hardening by Alexander Concha.
- Taxonomy query hardening by John Lamansky.
- Prevent sniffing out user names of non-authors by using canonical redirects. Props Verónica Valeros.
- Media security fixes by Richard Lundeen of Microsoft, Jesse Ou of Microsoft, and Microsoft Vulnerability Research.
- Improves file upload security on hosts with dangerous security settings.
- Cleans up old WordPress import files if the import does not finish.
- Introduce “clickjacking” protection in modern browsers on admin and login pages.
To check out the complete update info head on over to http://codex.wordpress.org/Version_3.1.3