An issue has been discovered in GitLab CE/EE affecting all versions starting from 14.0. It was possible to exploit a stored cross-site-scripting via a specifically crafted default branch name.
https://hackerone.com/reports/1256777
https://gitlab.com/gitlab-org/gitlab/-/issues/336460
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-22241.json