In all versions of GitLab CE/EE since version 13.6, it is possible to see pending invitations of any public group or public project by visiting an API endpoint.
{ "cpes": [ "cpe:2.3:a:gitlab:gitlab:*:*:*:*:community:*:*:*", "cpe:2.3:a:gitlab:gitlab:*:*:*:*:enterprise:*:*:*", "cpe:2.3:a:gitlab:gitlab:4.3.0:*:*:*:community:*:*:*", "cpe:2.3:a:gitlab:gitlab:4.3.0:*:*:*:enterprise:*:*:*", "cpe:2.3:a:gitlab:gitlab:*:*:*:*:*:*:*:*" ], "severity": "Medium" }