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.
An authorization issue relating to project maintainer impersonation was identified in GitLab EE 9.5 and later through 13.0.1 that could allow unauthorized users to impersonate as a maintainer to perform limited actions.
A security issue allowed achieving Denial of Service attacks through memory exhaustion by uploading malicious artifacts in all previous GitLab versions through 13.0.1