MediaWiki 1.22.x before 1.22.2, 1.21.x before 1.21.5, and 1.19.x before 1.19.11, when DjVu or PDF file upload support is enabled, allows remote attackers to execute arbitrary commands via shell metacharacters in (1) the page parameter to includes/media/DjVu.php; (2) the w parameter (aka width field) to thumb.php, which is not properly handled by includes/media/PdfHandler_body.php; and possibly unspecified vectors in (3) includes/media/Bitmap.php and (4) includes/media/ImageHandler.php.

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.

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.

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.

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 a \b (backspace) character in CSS.

Cross-site scripting (XSS) vulnerability in the ZeroRatedMobileAccess extension for MediaWiki 1.19.x before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 allows remote attackers to inject arbitrary web script or HTML via the "to" parameter to index.php.

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.

includes/resourceloader/ResourceLoaderContext.php in 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 obtain sensitive information via a "<" (open angle bracket) character in the lang parameter to w/load.php, which reveals the installation path in an error message.

(1) ApiBlock.php, (2) ApiCreateAccount.php, (3) ApiLogin.php, (4) ApiMain.php, (5) ApiQueryDeletedrevs.php, (6) ApiTokens.php, and (7) ApiUnblock.php in includes/api/ in MediaWiki 1.19.x before 1.19.8, 1.20.x before 1.20.7, and 1.21.x before 1.21.2 allow remote attackers to obtain CSRF tokens and bypass the cross-site request forgery (CSRF) protection mechanism via a JSONP request to wiki/api.php.