In all versions of GitLab CE/EE starting from 0.8.0 before 14.2.6, all versions starting from 14.3 before 14.3.4, and all versions starting from 14.4 before 14.4.1 certain Unicode characters can be abused to commit malicious code into projects without being noticed in merge request or source code viewer UI.
https://hackerone.com/reports/1280077
https://gitlab.com/gitlab-org/gitlab/-/issues/337193
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39908.json