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).
In the GlobalBlocking extension before 2020-03-10 for MediaWiki through 1.34.0, an issue related to IP range evaluation resulted in blocked users re-gaining escalated privileges. This is related to the case in which an IP address is contained in two ranges, one of which is locally disabled.
MediaWiki before 1.18.5, and 1.19.x before 1.19.2 saves passwords in the local database, (1) which could make it easier for context-dependent attackers to obtain cleartext passwords via a brute-force attack or, (2) when an authentication plugin returns a false in the strict function, could allow remote attackers to use old passwords for non-existing accounts in an external authentication system via unspecified vectors.
The CentralNotice extension for MediaWiki before 1.19.9, 1.20.x before 1.20.8, and 1.21.x before 1.21.3 sets the Cache-Control header to cache session cookies when a user is autocreated, which allows remote attackers to authenticate as the created user.
Cross-site scripting (XSS) vulnerability in MediaWiki 1.19.9 before 1.19.10, 1.2x before 1.21.4, and 1.22.x before 1.22.1 allows remote attackers to inject arbitrary web script or HTML via unspecified CSS values.
The CentralAuth extension for MediaWiki before 1.19.10, 1.2x before 1.21.4, and 1.22.x before 1.22.1 allows remote attackers to obtain usernames via vectors related to writing the names to the DOM of a page.
The Scribunto extension for MediaWiki allows remote attackers to obtain the rollback token and possibly other sensitive information via a crafted module, related to unstripping special page HTML.