GitLab Enterprise Edition (EE) before 8.17.7, 9.0.11, 9.1.8, 9.2.8, and 9.3.8 allows an authenticated user with the ability to create a project to use the mirroring feature to potentially read repositories belonging to other users.
GitLab before 8.14.9, 8.15.x before 8.15.6, and 8.16.x before 8.16.5 has XSS via a SCRIPT element in an issue attachment or avatar that is an SVG document.