I work on a team project for a test and maintenance course in University. We agreed as a team to adopt a git infrastructure that would prioritize the stability of the master branch at all cost by only updating commits up to the next stable point and tagging every single release. We have a long polling development branch to prepare our releases and we create feature branches for the tickets we need to resolve. I even wrote documentation to make sure that we don't forget and protected the master branch on gitlab from direct modifications.

Can someone fucking tell me how one of my teammates managed to fuck over all of this and work on an unfinished feature straight on master?

N.b. I know that he probably edited straight from gitlab's online text editor because they have a big where they don't restrict modifications on protected branches.