An issue was discovered in GitLab Community and Enterprise Edition through 12.2.1. Embedded images and media files in markdown could be pointed to an arbitrary server, which would reveal the IP address of clients requesting the file from that server.
https://gitlab.com/gitlab-org/gitlab-ce/issues/55115
https://about.gitlab.com/2019/08/29/security-release-gitlab-12-dot-2-dot-3-released/