MediaWiki 1.21/wmf12

The latest version (labeled "1.21wmf12") of MediaWiki, the software that powers Wikipedia and its sister sites, is being deployed to all Wikimedia sites in stages, starting on Monday, 18 March 2013 (see the roadmap).

We will continue to deploy the latest software every two weeks. This is intended to minimize disruption and possible issues, and make it easier to identify the cause of problems, since the possibly problematic code will be much more recent.

Most important changes

 * Security - - api.php?action=unblock returns the full user object
 * Security - - uselang=qqx can expose revision deleted data on log
 * - Provide an API to rotate an image
 * - Move the mediawiki.api.titleblacklist module to TitleBlacklist extension
 * - Enable on-wiki message language fallbacks
 * - Messages of log entries should support GENDER
 * - Add a link to Special:UserRights to Toolbox on user pages
 * - API uses non-unique value for paging for some modules

Breaking changes

 * Special:ActiveUsers was removed: 55807