In MediaWiki before 1.31.10 and 1.32.x through 1.34.x before 1.34.4, Special:UserRights exposes the existence of hidden users.

XSS exists in the MobileFrontend extension for MediaWiki before 1.34.4 because section.line is mishandled during regex section line replacement from PageGateway. Using crafted HTML, an attacker can elicit an XSS attack via jQuery's parseHTML method, which can cause image callbacks to fire even without the element being appended to the DOM.

An issue was discovered in the FileImporter extension for MediaWiki before 1.34.4. An attacker can import a file even when the target page is protected against "page creation" and the attacker should not be able to create it. This occurs because of a mishandled distinction between an upload restriction and a create restriction. An attacker cannot leverage this to overwrite anything, but can leverage this to force a wiki to have a page with a disallowed title.

An issue was discovered in MediaWiki 1.34.x before 1.34.4. On Special:Contributions, the NS filter uses unescaped messages as keys in the option key for an HTMLForm specifier. This is vulnerable to a mild XSS if one of those messages is changed to include raw HTML.

In MediaWiki before 1.31.8, 1.32.x and 1.33.x before 1.33.4, and 1.34.x before 1.34.2, private wikis behind a caching server using the img_auth.php image authorization security feature may have had their files cached publicly, so any unauthorized user could view them. This occurs because Cache-Control and Vary headers were mishandled.

resources/src/mediawiki.page.ready/ready.js in MediaWiki before 1.35 allows remote attackers to force a logout and external redirection via HTML content in a MediaWiki page.

The CentralAuth extension through REL1_34 for MediaWiki allows remote attackers to obtain sensitive hidden account information via an api.php?action=query&meta=globaluserinfo&guiuser= request. In other words, the information can be retrieved via the action API even though access would be denied when simply visiting wiki/Special:CentralAuth in a web browser.

In MediaWiki before 1.34.1, users can add various Cascading Style Sheets (CSS) classes (which can affect what content is shown or hidden in the user interface) to arbitrary DOM nodes via HTML content within a MediaWiki page. This occurs because jquery.makeCollapsible allows applying an event handler to any Cascading Style Sheets (CSS) selector. There is no known way to exploit this for cross-site scripting (XSS).

An issue was discovered in the AbuseFilter extension for MediaWiki. includes/special/SpecialAbuseLog.php allows attackers to obtain sensitive information, such as deleted/suppressed usernames and summaries, from AbuseLog revision data. This affects REL1_32 and REL1_33.

An issue was discovered in the CheckUser extension through 1.35.0 for MediaWiki. Oversighted edit summaries are still visible in CheckUser results in violation of MediaWiki's permissions model.