An issue was discovered in GitLab Community and Enterprise Edition before 11.7.10, 11.8.x before 11.8.6, and 11.9.x before 11.9.4. A regex input validation issue for the .gitlab-ci.yml refs value allows Uncontrolled Resource Consumption.
https://gitlab.com/gitlab-org/gitlab-ce/issues/49665
https://about.gitlab.com/blog/categories/releases/
https://about.gitlab.com/2019/04/01/security-release-gitlab-11-dot-9-dot-4-released/