GitLab has remediated an issue in GitLab CE/EE affecting all versions from 15.10 before 19.3.6, 19.4 before 19.4.3, and 19.5 before 19.5.1 that, could have allowed an authenticated to read milestone metadata, including titles, descriptions, and full project paths, from arbitrary private projects across the instance without any project membership, due to missing authorization checks on a user-supplied project filter parameter in the group milestones API.