GitLab has remediated an issue in GitLab CE/EE affecting all versions from 17.11 before 18.6.6, 18.7 before 18.7.4, and 18.8 before 18.8.4 that, under certain conditions could have allowed an authenticated user to view certain pipeline values by querying the API.
Upgrade to versions 18.6.6, 18.7.4, 18.8.4 or above.