An issue has been discovered in GitLab CE/EE affecting all versions from 16.11 before 18.1.6, 18.2 before 18.2.6, and 18.3 before 18.3.2 that could have allowed authenticated users to make unintended internal requests through proxy environments by injecting crafted sequences.
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.