An issue was discovered in the VisualEditor extension in MediaWiki before 1.31.13, and 1.32.x through 1.35.x before 1.35.2. . When using VisualEditor to edit a MediaWiki user page belonging to an existing, but hidden, user, VisualEditor will disclose that the user exists. (It shouldn't because they are hidden.) This is related to ApiVisualEditor.
An issue was discovered in the GrowthExperiments extension for MediaWiki through 1.39.3. The UserImpactHandler for GrowthExperiments inadvertently returns the timezone preference for arbitrary users, which can be used to de-anonymize users.
An issue was discovered in the CheckUser extension for MediaWiki through 1.39.3. When a user with checkuserlog permissions makes many CheckUserLog API requests in some configurations, denial of service can occur (RequestTimeoutException or upstream request timeout).
An issue was discovered in the GrowthExperiments extension for MediaWiki through 1.39.3. Attackers might be able to see edits for which the username has been hidden, because there is no check for rev_deleted.
An issue was discovered in MediaWiki before 1.35.10, 1.36.x through 1.38.x before 1.38.6, and 1.39.x before 1.39.3. An auto-block can occur for an untrusted X-Forwarded-For header.
An issue was discovered in MediaWiki before 1.35.9, 1.36.x through 1.38.x before 1.38.5, and 1.39.x before 1.39.1. There is XSS in Wikibase date formatting via wikibase-time-precision-* fields. This allows JavaScript execution by staff/admin users who do not intentionally have the editsitejs capability.
An issue was discovered in MediaWiki before 1.35.9, 1.36.x through 1.38.x before 1.38.5, and 1.39.x before 1.39.1. CheckUser TokenManager insecurely uses AES-CTR encryption with a repeated (aka re-used) nonce, allowing an adversary to decrypt.
An issue was discovered in MediaWiki before 1.35.9, 1.36.x through 1.38.x before 1.38.5, and 1.39.x before 1.39.1. When installing with a pre-existing data directory that has weak permissions, the SQLite files are created with file mode 0644, i.e., world readable to local users. These files include credentials data.
In the GrowthExperiments extension for MediaWiki through 1.39, the growthmanagementorlist API allows blocked users (blocked in ApiManageMentorList) to enroll as mentors or edit any of their mentorship-related properties.
An issue was discovered in MediaWiki before 1.35.9, 1.36.x through 1.38.x before 1.38.5, and 1.39.x before 1.39.1. SpecialMobileHistory allows remote attackers to cause a denial of service because database queries are slow.