GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
If you go to http://bad.neon2.ml/ on tor, the browser will become unresponsive. I attached the website sorce code to this bug report. This user on twitter claims to of created this exploit. https://twitter.com/ceaec