Description
Jenkins 2.196 and earlier, LTS 2.176.3 and earlier printed the value of the "Cookie" HTTP request header on the /whoAmI/ URL, allowing attackers exploiting another XSS vulnerability to obtain the HTTP session cookie despite it being marked HttpOnly.
Remediation
References
http://www.openwall.com/lists/oss-security/2019/09/25/3
https://jenkins.io/security/advisory/2019-09-25/#SECURITY-1505