An Information Exposure issue (issue 2 of 2) was discovered in GitLab Community and Enterprise Edition before 11.7.8, 11.8.x before 11.8.4, and 11.9.x before 11.9.2. During the OAuth authentication process, the application attempts to validate a parameter in an insecure way, potentially exposing data.
https://gitlab.com/gitlab-org/gitlab-ee/issues/9729
https://about.gitlab.com/blog/categories/releases/
https://about.gitlab.com/2019/04/01/security-release-gitlab-11-dot-9-dot-4-released/