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.

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.

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.