Description
In Jenkins 2.196 and earlier, LTS 2.176.3 and earlier, the f:expandableTextBox form control interpreted its content as HTML when expanded, resulting in a stored XSS vulnerability exploitable by users with permission to define its contents (typically Job/Configure).
Remediation
References
https://jenkins.io/security/advisory/2019-09-25/#SECURITY-1498
http://www.openwall.com/lists/oss-security/2019/09/25/3