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).

In the GlobalBlocking extension before 2020-03-10 for MediaWiki through 1.34.0, an issue related to IP range evaluation resulted in blocked users re-gaining escalated privileges. This is related to the case in which an IP address is contained in two ranges, one of which is locally disabled.

MediaWiki through 1.33.1 allows attackers to bypass the Title_blacklist protection mechanism by starting with an arbitrary title, establishing a non-resolvable redirect for the associated page, and using redirect=1 in the action API when editing that page.

In MediaWiki through 1.33.0, Special:Redirect allows information disclosure of suppressed usernames via a User ID Lookup.

Wikimedia MediaWiki through 1.32.1 allows CSRF.

An Incorrect Access Control vulnerability was found in Wikimedia MediaWiki 1.27.0 through 1.32.1. Directly POSTing to Special:ChangeEmail would allow for bypassing re-authentication, allowing for potential account takeover.