GitLab has remediated an issue in GitLab CE/EE affecting all versions from 15.0 before 19.3.6, 19.4 before 19.4.3, and 19.5 before 19.5.1 that, when a merge request in a public project referenced a confidential issue from a private project, an authenticated user with no project membership could have read the confidential issue's title, due to a viewer-independent fragment cache key that incorrectly shared per-user-redacted rendered content across all users.
https://hackerone.com/reports/3963293
https://gitlab.com/gitlab-org/gitlab/-/work_items/632207
https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-107674
https://docs.gitlab.com/releases/patches/patch-release-gitlab-19-5-1-released/