An issue has been discovered in GitLab affecting all versions starting with 13.10. GitLab was vulnerable to a stored XSS in blob viewer of notebooks.
https://hackerone.com/reports/1060114
https://gitlab.com/gitlab-org/gitlab/-/issues/294128
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-22220.json