An issue was discovered in the CheckUser extension for MediaWiki through 1.42.1. The API can expose suppressed information for log events. (The log_deleted attribute is not applied to entries.)
An issue was discovered in the ArticleRatings extension for MediaWiki through 1.42.1. Special:ChangeRating allows CSRF to alter data via a GET request.
An issue was discovered in includes/specials/SpecialMovePage.php in MediaWiki before 1.39.7, 1.40.x before 1.40.3, and 1.41.x before 1.41.1. If a user with the necessary rights to move the page opens Special:MovePage for a page with tens of thousands of subpages, then the page will exceed the maximum request time, leading to a denial of service.
An issue was discovered in includes/CommentFormatter/CommentParser.php in MediaWiki before 1.39.7, 1.40.x before 1.40.3, and 1.41.x before 1.41.1. XSS can occur because of mishandling of the 0x1b character, as demonstrated by Special:RecentChanges#%1b0000000.