GitLab EE 12.3 through 12.5, 12.4.3, and 12.3.6 allows Denial of Service. Certain characters were making it impossible to create, edit, or view issues and commits.
https://gitlab.com/gitlab-org/gitlab/issues/14947
https://about.gitlab.com/blog/categories/releases/
https://about.gitlab.com/blog/2019/11/27/security-release-gitlab-12-5-1-released/