An issue was discovered in GitLab Community and Enterprise Edition before 11.1.7, 11.2.x before 11.2.4, and 11.3.x before 11.3.1. Remote attackers could obtain sensitive information about issues, comments, and project titles via events API insecure direct object reference.
https://about.gitlab.com/releases/2018/10/01/security-release-gitlab-11-dot-3-dot-1-released/