For GitLab before 13.0.12, 13.1.6, 13.2.3 a cross-site scripting (XSS) vulnerability exists in the issue reference number tooltip.
https://hackerone.com/reports/831962
https://gitlab.com/gitlab-org/gitlab/-/issues/212626
https://gitlab.com/gitlab-org/cves/-/blob/master/2020/CVE-2020-13285.json