MediaWiki before 1.15.2 does not prevent wiki editors from linking to images from other web sites in wiki pages, which allows editors to obtain IP addresses and other information of wiki users by adding a link to an image on an attacker-controlled web site, aka "CSS validation issue."

Multiple cross-site scripting (XSS) vulnerabilities in the web-based installer (config/index.php) in MediaWiki 1.6 before 1.6.12, 1.12 before 1.12.4, and 1.13 before 1.13.4, when the installer is in active use, allow remote attackers to inject arbitrary web script or HTML via unspecified vectors.

MediaWiki 1.11, and other versions before 1.13.3, does not properly protect against the download of backups of deleted images, which might allow remote attackers to obtain sensitive information via requests for files in images/deleted/.

MediaWiki 1.8.1, and other versions before 1.13.3, when the wgShowExceptionDetails variable is enabled, sometimes provides the full installation path in a debugging message, which might allow remote attackers to obtain sensitive information via unspecified requests that trigger an uncaught exception.