An issue was discovered in Special:MediaSearch in the MediaSearch extension in MediaWiki through 1.36.2. The suggestion text (a parameter to mediasearch-did-you-mean) was not being properly sanitized and allowed for the injection and execution of HTML and JavaScript via the intitle: search operator within the query.
An issue was discovered in the Mentor dashboard in the GrowthExperiments extension in MediaWiki through 1.36.2. The Growthexperiments-mentor-dashboard-mentee-overview-add-filter-total-edits-headline, growthexperiments-mentor-dashboard-mentee-overview-add-filter-starred-headline, growthexperiments-mentor-dashboard-mentee-overview-info-text, growthexperiments-mentor-dashboard-mentee-overview-info-legend-headline, and growthexperiments-mentor-dashboard-mentee-overview-active-ago MediaWiki messages were not being properly sanitized and allowed for the injection and execution of HTML and JavaScript.
In MediaWiki before 1.31.15, 1.32.x through 1.35.x before 1.35.3, and 1.36.x before 1.36.1, bots have certain unintended API access. When a bot account has a "sitewide block" applied, it is able to still "purge" pages through the MediaWiki Action API (which a "sitewide block" should have prevented).