An issue was discovered in the Growth extension in MediaWiki through 1.36.2. On any Wiki with the Mentor Dashboard feature enabled, users can login with a mentor account and trigger an XSS payload (such as alert) via Growthexperiments-mentor-dashboard-mentee-overview-no-js-fallback.

An issue was discovered in the GlobalWatchlist extension in MediaWiki through 1.36.2. The rev-deleted-user and ntimes messages were not properly escaped and allowed for users to inject HTML and JavaScript.

An issue was discovered in SecurePoll in the Growth extension in MediaWiki through 1.36.2. Simple polls allow users to create alerts by changing their User-Agent HTTP header and submitting a vote.

A denial-of-service issue was discovered in MediaWiki 1.37.x before 1.37.2. Rendering of w/index.php?title=Special%3AWhatLinksHere&target=Property%3AP31&namespace=1&invert=1 can take more than thirty seconds. There is a DDoS risk.

An issue was discovered in MediaWiki before 1.35.6, 1.36.x before 1.36.4, and 1.37.x before 1.37.2. Users with the editinterface permission can trigger infinite recursion, because a bare local interwiki is mishandled for the mainpage message.

A denial-of-service issue was discovered in MediaWiki before 1.35.6, 1.36.x before 1.36.4, and 1.37.x before 1.37.2. When many files exist, requesting Special:NewFiles with actor as a condition can result in a very long running query.

An issue was discovered in the MediaWiki through 1.38.2. The community configuration pages for the GrowthExperiments extension could cause a site to become unavailable due to insufficient validation when certain actions (including page moves) were performed.

An issue was discovered in MediaWiki before 1.37.3 and 1.38.x before 1.38.1. The contributions-title, used on Special:Contributions, is used as page title without escaping. Hence, in a non-default configuration where a username contains HTML entities, it won't be escaped.

An issue was discovered in MediaWiki before 1.35.7, 1.36.x and 1.37.x before 1.37.3, and 1.38.x before 1.38.1. XSS can occur in configurations that allow a JavaScript payload in a username. After account creation, when it sets the page title to "Welcome" followed by the username, the username is not escaped: SpecialCreateAccount::successfulAction() calls ::showSuccessPage() with a message as second parameter, and OutputPage::setPageTitle() uses text().

An issue was discovered in MediaWiki through 1.38.1. The lemma length of a Wikibase lexeme is currently capped at a thousand characters. Unfortunately, this length is not validated, allowing much larger lexemes to be created, which introduces various denial-of-service attack vectors within the Wikibase and WikibaseLexeme extensions. This is related to Special:NewLexeme and Special:NewProperty.