includes/upload/UploadBase.php in MediaWiki before 1.19.12, 1.20.x and 1.21.x before 1.21.6, and 1.22.x before 1.22.3 does not prevent use of invalid namespaces in SVG files, which allows remote attackers to conduct cross-site scripting (XSS) attacks via an SVG upload, as demonstrated by use of a W3C XHTML namespace in conjunction with an IFRAME element.

The CentralAuth extension for MediaWiki 1.19.x before 1.19.8, 1.20.x before 1.20.7, and 1.21.x before 1.21.2 caches a valid CentralAuthUser object in the centralauth_User cookie even when a user has not successfully logged in, which allows remote attackers to bypass authentication without a password.

The CleanChanges extension for MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3, when "Group changes by page in recent changes and watchlist" is enabled, allows remote attackers to obtain sensitive information (revision-deleted IPs) via the Recent Changes page.

Incomplete blacklist vulnerability in Sanitizer::checkCss in MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 allows remote attackers to conduct cross-site scripting (XSS) attacks via certain non-ASCII characters in CSS, as demonstrated using variations of "expression" containing (1) full width characters or (2) IPA extensions, which are converted and rendered by Internet Explorer.

Incomplete blacklist vulnerability in Sanitizer::checkCss in MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 allows remote attackers to conduct cross-site scripting (XSS) attacks via a \b (backspace) character in CSS.

Cross-site request forgery (CSRF) vulnerability in the CentralAuth extension for MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 allows remote attackers to hijack the authentication of users for requests that login via vectors involving image loading.

Unrestricted file upload vulnerability in the chunk upload API in MediaWiki 1.19 through 1.19.6 and 1.20.x before 1.20.6 allows remote attackers to execute arbitrary code by uploading a file with an executable extension.

MediaWiki before 1.19.6 and 1.20.x before 1.20.5 does not allow extensions to prevent password changes without using both Special:PasswordReset and Special:ChangePassword, which allows remote attackers to bypass the intended restrictions of an extension that only implements one of these blocks.

MediaWiki before 1.19.6 and 1.20.x before 1.20.5 allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated by a CDATA section containing valid UTF-7 encoded sequences in a SVG file, which is then incorrectly interpreted as UTF-8 by Chrome and Firefox.

Cross-site scripting (XSS) vulnerability in pages/TalkpageHistoryView.php in the LiquidThreads (LQT) extension 2.x and possibly 3.x for MediaWiki 1.19.x before 1.19.8, 1.20.x before 1.20.7, and 1.21.x before 1.21.2 allows remote attackers to inject arbitrary web script or HTML via a thread subject.

Multiple cross-site scripting (XSS) vulnerabilities in repo/includes/EntityView.php in the Wikibase extension for MediaWiki 1.19.x before 1.19.8, 1.20.x before 1.20.7, and 1.21.x before 1.21.2 allow (1) remote attackers to inject arbitrary web script or HTML via a label in the "In other languages" section or (2) remote administrators to inject arbitrary web script or HTML via a description.

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.