A vulnerability was discovered in GitLab versions before 13.1.10, 13.2.8 and 13.3.4. When 2 factor authentication was enabled for groups, a malicious user could bypass that restriction by sending a specific query to the API endpoint.
https://hackerone.com/reports/691592
https://gitlab.com/gitlab-org/gitlab/-/issues/32215
https://gitlab.com/gitlab-org/cves/-/blob/master/2020/CVE-2020-13297.json