Incorrect Authorization in GitLab CE/EE 13.4 or above allows a user with guest membership in a project to modify the severity of an incident.
https://hackerone.com/reports/1341674
https://gitlab.com/gitlab-org/gitlab/-/issues/341479
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39902.json