CVE-2021-22182: 
GitLab vulnerability analysis and mitigation

An issue was discovered in GitLab affecting all versions starting with 13.7, where GitLab was vulnerable to a stored Cross-Site Scripting (XSS) in merge requests. The vulnerability was reported through GitLab's HackerOne bug bounty program and was assigned CVE-2021-22182 (GitLab Security Release, CVE Details).

The vulnerability allowed an attacker to inject malicious scripts through the target branch section when creating a merge request. The XSS payload would be stored and executed when users viewed the merge request, particularly when clicking the 'Merge Immediately' button. While GitLab.com was protected due to Content Security Policy (CSP), self-hosted instances without proper CSP configuration were vulnerable (GitLab Issue).

The stored XSS vulnerability could be exploited in public projects where merge requests are accessible to everyone. When triggered, the malicious script would execute in the context of other users viewing the merge request, potentially leading to session hijacking, data theft, or other malicious actions (GitLab Security Release).

The vulnerability could be exploited by creating a merge request with a specially crafted target branch name containing XSS payload. The exploit was confirmed to work in public projects, making it accessible to any authenticated user with the ability to create merge requests (GitLab Issue).

The vulnerability was patched in GitLab versions 13.8.2, 13.7.6, and 13.6.6. GitLab strongly recommended that all installations running affected versions be upgraded to one of these patched versions immediately. Additionally, implementing proper Content Security Policy (CSP) could help mitigate such XSS attacks (GitLab Security Release).