Cross-site scripting (XSS) vulnerability in MediaWiki before 1.16.4, when Internet Explorer 6 or earlier is used, allows remote attackers to inject arbitrary web script or HTML via an uploaded file accessed with a dangerous extension such as .html located before a ? (question mark) in a query string, in conjunction with a modified URI path that has a %2E sequence in place of the . (dot) character. NOTE: this vulnerability exists because of an incomplete fix for CVE-2011-1578.

The transwiki import functionality in MediaWiki before 1.16.3 does not properly check privileges, which allows remote authenticated users to perform imports from any wgImportSources wiki via a crafted POST request.

The checkCss function in includes/Sanitizer.php in the wikitext parser in MediaWiki before 1.16.3 does not properly validate Cascading Style Sheets (CSS) token sequences, which allows remote attackers to conduct cross-site scripting (XSS) attacks or obtain sensitive information by using the \2f\2a and \2a\2f hex strings to surround CSS comments.