GitLab EE, versions 11.4 before 11.4.8 and 11.5 before 11.5.1, is affected by an insecure direct object reference vulnerability that permits an unauthorized user to publish the draft merge request comments of another user.
https://gitlab.com/gitlab-org/gitlab-ee/issues/8180
https://about.gitlab.com/2018/11/28/security-release-gitlab-11-dot-5-dot-1-released/