Mattermost allows authenticated guest users to enumerate user IDs outside their allowed visibility scope

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint. Mattermost Advisory ID: MMSA-2026-00594.