Description
Jenkins 2.196 and earlier, LTS 2.176.3 and earlier did not escape the reason why a queue items is blcoked in tooltips, resulting in a stored XSS vulnerability exploitable by users able to control parts of the reason a queue item is blocked, such as label expressions not matching any idle executors.
Remediation
References
http://www.openwall.com/lists/oss-security/2019/09/25/3
https://jenkins.io/security/advisory/2019-09-25/#SECURITY-1537%20%282%29