Gitlab Community Edition version 10.3 is vulnerable to an improper authorization issue in the Oauth sign-in component resulting in unauthorized user login.
https://www.debian.org/security/2018/dsa-4145
https://gitlab.com/gitlab-org/gitlab-ce/issues/32198
https://about.gitlab.com/2018/01/16/gitlab-10-dot-3-dot-4-released/