An access control issue exists in < 12.3.5, < 12.2.8, and < 12.1.14 for GitLab Community Edition (CE) and Enterprise Edition (EE) where private merge requests and issues would be disclosed with the Group Search feature provided by Elasticsearch integration
https://hackerone.com/reports/701144
https://about.gitlab.com/releases/2019/10/07/security-release-gitlab-12-dot-3-dot-5-released/