An issue was discovered in GitLab Community and Enterprise Edition before 11.8.9, 11.9.x before 11.9.10, and 11.10.x before 11.10.2. It has a Race Condition which could allow users to approve a merge request multiple times and potentially reach the approval count required to merge.
https://gitlab.com/gitlab-org/gitlab-ee/issues/10357
https://about.gitlab.com/2019/04/29/security-release-gitlab-11-dot-10-dot-2-released/