CVE-2021-21665: CSRF vulnerability in Jenkins XebiaLabs XL Deploy Plugin allows capturing credentials

The vulnerability stems from a form validation endpoint that 1) accepted GET requests (CSRFable) 2) used insufficient permission checks (Overall/Read instead of Administer). In Jenkins plugins, form validation methods like 'doCheck...' or 'descriptorByName' endpoints are common patterns. The advisory specifically mentions the form validation method was the attack vector, and the fix added POST requirements and Administer permissions. While exact function names aren't provided, this reconstruction matches Jenkins plugin architecture and the vulnerability description.