Cross-site scripting (XSS) vulnerability in the ZeroRatedMobileAccess extension for MediaWiki 1.19.x before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 allows remote attackers to inject arbitrary web script or HTML via the "to" parameter to index.php.
https://bugzilla.wikimedia.org/show_bug.cgi?id=55991
http://secunia.com/advisories/55754
http://lists.wikimedia.org/pipermail/mediawiki-announce/2013-November/000135.html