Cross-site scripting (XSS) vulnerability in the outputPage function in includes/SkinTemplate.php in MediaWiki before 1.17.5, 1.18.x before 1.18.4, and 1.19.x before 1.19.1 allows remote attackers to inject arbitrary web script or HTML via the uselang parameter to index.php/Main_page.
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.
MediaWiki before 1.17.1 allows remote attackers to obtain the page titles of all restricted pages via a series of requests involving the (1) curid or (2) oldid parameter.