GitLab 8.3 through 12.8.1 allows Information Disclosure. It was possible for certain non-members to access the Contribution Analytics page of a private group.
GitLab before 12.8.2 has Incorrect Access Control. It was internally discovered that the LFS import process could potentially be used to incorrectly access LFS objects not owned by the user.
GitLab 12.2.2 and below contains a security vulnerability that allows a guest user in a private project to see the merge request ID associated to an issue via the activity timeline.
An issue was discovered in GitLab Enterprise Edition (EE) 8.9.0 through 12.6.1. Using the project import feature, it was possible for someone to obtain issues from private projects.