Cross-site scripting (XSS) vulnerability in the Html class in MediaWiki before 1.19.24, 1.2x before 1.23.9, and 1.24.x before 1.24.2 allows remote attackers to inject arbitrary web script or HTML via a LanguageConverter substitution string when using a language variant.
https://lists.wikimedia.org/pipermail/mediawiki-announce/2015-March/000175.html
https://phabricator.wikimedia.org/T73394
https://security.gentoo.org/glsa/201510-05
http://www.mandriva.com/security/advisories?name=MDVSA-2015:200