MGASA-2021-0086

In MediaWiki before 1.31.11, the messages userrights-expiry-current and userrights-expiry-none can contain raw HTML. XSS can happen when a user visits Special:UserRights but does not have rights to change all userrights, and the table on the left side has unchangeable groups in it. The right column with the changeable groups is not affected and is escaped correctly (CVE-2020-35475).

MediaWiki before 1.31.11 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 (CVE-2020-35477).

MediaWiki before 1.31.11 allows XSS via BlockLogFormatter.php. Language::translateBlockExpiry itself does not escape in all code paths. For example, the return of Language::userTimeAndDate is is always unsafe for HTML in a month value (CVE-2020-35479).

An issue was discovered in MediaWiki before 1.31.11. Missing users (accounts that don't exist) and hidden users (accounts that have been explicitly hidden due to being abusive, or similar) that the viewer cannot see are handled differently, exposing sensitive information about the hidden status to unprivileged viewers. This exists on various code paths (CVE-2020-35480).