GitLab has remediated an issue in GitLab CE/EE affecting all versions from 11.2 before 18.9.6, 18.10 before 18.10.4, and 18.11 before 18.11.1 that under certain conditions could have allowed an authenticated user with project owner permissions to bypass group fork prevention settings due to improper authorization checks.
https://hackerone.com/reports/3275222
https://gitlab.com/gitlab-org/gitlab/-/work_items/567781
https://about.gitlab.com/releases/2026/04/22/patch-release-gitlab-18-11-1-released/