MediaWiki before 1.5.4 uses a hard-coded "internal placeholder string", which allows remote attackers to bypass protection against cross-site scripting (XSS) attacks and execute Javascript using inline style attributes, which are processed by Internet Explorer.
https://exchange.xforce.ibmcloud.com/vulnerabilities/23882
http://www.vupen.com/english/advisories/2005/3059
http://www.securityfocus.com/bid/16032
http://www.mediawiki.org/wiki/Download
http://secunia.com/advisories/18717
http://secunia.com/advisories/18219
http://lists.suse.com/archive/suse-security-announce/2006-Feb/0001.html