GitLab 12.7 through 12.8.1 has Insecure Permissions. Under certain conditions involving groups, project authorization changes were not being applied.
https://about.gitlab.com/releases/2020/03/04/gitlab-12-dot-8-dot-2-released/index.html
https://about.gitlab.com/releases/2020/03/04/gitlab-12-dot-8-dot-2-released/