An issue was discovered in MediaWiki before 1.35.5, 1.36.x before 1.36.3, and 1.37.x before 1.37.1. A title blocked by AbuseFilter can be created via Special:ChangeContentModel due to the mishandling of the EditFilterMergedContent hook return value.
An issue was discovered in the SportsTeams extension for MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.40.1. SportsTeams: Special:SportsManagerLogo and Special:SportsTeamsManagerLogo do not check for the sportsteamsmanager user right, and thus an attacker may be able to affect pages that are concerned with sports teams.
In MediaWiki through 1.37, blocked IP addresses are allowed to edit EntitySchema items.
An issue was discovered in the SportsTeams extension for MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.40.1. It does not check for the anti-CSRF edit token in Special:SportsTeamsManager and Special:UpdateFavoriteTeams.
An issue was discovered in the Wikibase extension for MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.40.1. During item merging, ItemMergeInteractor does not have an edit filter running (e.g., AbuseFilter).
MediaWiki before 1.35.1 blocks legitimate attempts to hide log entries in some situations. If one sets MediaWiki:Mainpage to Special:MyLanguage/Main Page, visits a log entry on Special:Log, and toggles the "Change visibility of selected log entries" checkbox (or a tags checkbox) next to it, there is a redirection to the main page's action=historysubmit (instead of the desired behavior in which a revision-deletion form appears).
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).
An issue was discovered in MediaWiki before 1.35.11, 1.36.x through 1.38.x before 1.38.7, 1.39.x before 1.39.4, and 1.40.x before 1.40.1. It is possible to bypass the Bad image list (aka badFile) by using the thumb parameter (aka Manualthumb) of the File syntax.