An issue has been discovered in GitLab affecting all versions starting from 9.3 before 15.4.6, all versions starting from 15.5 before 15.5.5, all versions starting from 15.6 before 15.6.1. It was possible for a project maintainer to leak a webhook secret token by changing the webhook URL to an endpoint that allows them to capture request headers.
Published January 26, 2023.