A user with an unverified email address could request an access to domain restricted groups in GitLab EE 12.2 and later through 13.0.1
https://hackerone.com/reports/806255
https://gitlab.com/gitlab-org/gitlab/-/issues/209254
https://gitlab.com/gitlab-org/cves/-/blob/master/2020/CVE-2020-13275.json