For GitLab before 13.0.12, 13.1.6, 13.2.3 after a group transfer occurs, members from a parent group keep their access level on the subgroup leading to improper access.
https://hackerone.com/reports/790786
https://gitlab.com/gitlab-org/gitlab/-/issues/202687
https://gitlab.com/gitlab-org/cves/-/blob/master/2020/CVE-2020-13282.json