GitLab CE/EE before 11.3.12, 11.4.x before 11.4.10, and 11.5.x before 11.5.3 allows Directory Traversal in Templates API.
https://gitlab.com/gitlab-org/gitlab-ce/issues/54857
https://about.gitlab.com/2018/12/06/critical-security-release-gitlab-11-dot-5-dot-3-released/