Cross-site scripting (XSS) vulnerability in MediaWiki before 1.19.10, 1.2x before 1.21.4, and 1.22.x before 1.22.1 allows remote attackers to inject arbitrary web script or HTML via a -o-link attribute.
http://lists.wikimedia.org/pipermail/mediawiki-announce/2014-January/000138.html