Jenkins did not escape the reason a queue item is blocked in tooltips. This resulted in a cross-site scripting vulnerability exploitable by attackers able to control the reason a queue item is blocked, for example a label expression that does not match idle executors. References: https://jenkins.io/security/advisory/2019-09-25/#SECURITY-1537%20(2)
Created jenkins tracking bugs for this issue: Affects: fedora-all [bug 1764477]