An issue was discovered in the CheckUser extension for MediaWiki through 1.42.1. The Special:Investigate feature can expose suppressed information for log events. (TimelineService does not support properly suppressing.)

Citizen is a MediaWiki skin that makes extensions part of the cohesive experience. The page `MediaWiki:Tagline` has its contents used unescaped, so custom HTML (including Javascript) can be injected by someone with the ability to edit the MediaWiki namespace (typically those with the `editinterface` permission, or sysops). This vulnerability is fixed in 2.16.0.

An issue was discovered in the GlobalBlocking extension in MediaWiki before 1.40.2. For a Special:GlobalBlock?uselang=x-xss URI, i18n-based XSS can occur via the parentheses message. This affects subtitle links in buildSubtitleLinks.

An issue was discovered in the Phonos extension in MediaWiki before 1.40.2. PhonosButton.js allows i18n-based XSS via the phonos-purge-needed-error message.

An issue was discovered in the WatchAnalytics extension in MediaWiki before 1.40.2. XSS can occur via the Special:PageStatistics page parameter.

An issue was discovered in the PageTriage extension in MediaWiki before 1.35.14, 1.36.x through 1.39.x before 1.39.6, and 1.40.x before 1.40.2. XSS can occur via the rev-deleted-user, pagetriage-tags-quickfilter-label, pagetriage-triage, pagetriage-filter-date-range-format-placeholder, pagetriage-filter-date-range-to, pagetriage-filter-date-range-from, pagetriage-filter-date-range-heading, pagetriage-filter-set-button, or pagetriage-filter-reset-button message.

An issue was discovered in the Cargo extension in MediaWiki before 1.35.14, 1.36.x through 1.39.x before 1.39.6, and 1.40.x before 1.40.2. The Special:Drilldown page allows XSS via artist, album, and position parameters because of applied filter values in drilldown/CargoAppliedFilter.php.

An issue was discovered in the CheckUser extension in MediaWiki before 1.35.14, 1.36.x through 1.39.x before 1.39.6, and 1.40.x before 1.40.2. XSS can occur via message definitions. e.g., in SpecialCheckUserLog.

An issue was discovered in the CampaignEvents extension in MediaWiki before 1.35.14, 1.36.x through 1.39.x before 1.39.6, and 1.40.x before 1.40.2. The Special:EventDetails page allows XSS via the x-xss language setting for internationalization (i18n).

An issue was discovered in MediaWiki before 1.35.14, 1.36.x through 1.39.x before 1.39.6, and 1.40.x before 1.40.2. In includes/logging/RightsLogFormatter.php, group-*-member messages can result in XSS on Special:log/rights.