MediaWiki before 1.17.1 does not check for read permission before handling action=ajax requests, which allows remote attackers to obtain sensitive information by (1) leveraging the SpecialUpload::ajaxGetExistsWarning function, or by (2) leveraging an extension, as demonstrated by the CategoryTree, ExtTab, and InlineEditor extensions.

References

• https://nvd.nist.gov/vuln/detail/CVE-2011-4361
• https://bugzilla.redhat.com/show_bug.cgi?id=758171
• https://bugzilla.wikimedia.org/show_bug.cgi?id=32616
• http://lists.wikimedia.org/pipermail/mediawiki-announce/2011-November/000104.html
• http://openwall.com/lists/oss-security/2011/11/29/12
• http://openwall.com/lists/oss-security/2011/11/29/6
• http://www.debian.org/security/2011/dsa-2366