An issue was discovered in GitLab Community and Enterprise Edition before 11.4.13, 11.5.x before 11.5.6, and 11.6.x before 11.6.1. It has Incorrect Access Control (issue 2 of 6).
https://about.gitlab.com/blog/categories/releases/
https://about.gitlab.com/2018/12/31/security-release-gitlab-11-dot-6-dot-1-released/