GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.2 before 18.10.7, 18.11 before 18.11.4, and 19.0 before 19.0.1 that under certain conditions could have allowed an unauthorized user to enumerate private projects due to incorrect authorization checks.
Upgrade to versions 18.10.7, 18.11.4, 19.0.1 or above.