An issue has been discovered in GitLab affecting all versions starting with 12.9. GitLab was vulnerable to a stored XSS if scoped labels were used.
https://hackerone.com/reports/1050189
https://gitlab.com/gitlab-org/gitlab/-/issues/291004
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-22199.json