includes/resourceloader/ResourceLoaderContext.php in MediaWiki 1.19.x before 1.19.8, 1.20.x before 1.20.7, and 1.21.x before 1.21.2 allows remote attackers to obtain sensitive information via a “<” (open angle bracket) character in the lang parameter to w/load.php, which reveals the installation path in an error message.
lists.wikimedia.org/pipermail/mediawiki-announce/2013-September/000133.html
osvdb.org/96913
seclists.org/oss-sec/2013/q3/553
secunia.com/advisories/54715
bugzilla.wikimedia.org/show_bug.cgi?id=46332
exchange.xforce.ibmcloud.com/vulnerabilities/86895
www.mediawiki.org/wiki/Release_notes/1.19
www.mediawiki.org/wiki/Release_notes/1.20
www.mediawiki.org/wiki/Release_notes/1.21