Multiple cross-site scripting (XSS) vulnerabilities in MediaWiki before 1.18.5 and 1.19.x before 1.19.2, when unspecified JavaScript gadgets are used, allow remote attackers to inject arbitrary web script or HTML via the userlang parameter to w/index.php.
https://phabricator.wikimedia.org/T39587
https://lists.wikimedia.org/pipermail/mediawiki-announce/2012-August/000119.html
https://bugzilla.redhat.com/show_bug.cgi?id=853417
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=686330