Eval injection vulnerability in MediaWiki 1.5.x before 1.5.3 allows remote attackers to execute arbitrary PHP code via the "user language option," which is used as part of a dynamic class name that is processed using the eval function.
http://www.vupen.com/english/advisories/2005/2726
http://www.securityfocus.com/bid/15703
http://www.kb.cert.org/vuls/id/392156
http://sourceforge.net/project/shownotes.php?group_id=34373&release_id=375755