MediaWiki before 1.19.4 and 1.20.x before 1.20.3 contains an error in the api.php script which allows remote attackers to obtain sensitive information.
https://security-tracker.debian.org/tracker/CVE-2013-1817
https://exchange.xforce.ibmcloud.com/vulnerabilities/88359
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2013-1817
http://www.securityfocus.com/bid/58305