In Jenkins 2.355 and earlier, LTS 2.332.3 and earlier, an observable timing discrepancy on the login form allows distinguishing between login attempts with an invalid username, and login attempts with a valid username and wrong password, when using the Jenkins user database security realm.

In Jenkins 2.320 through 2.355 (both inclusive) and LTS 2.332.1 through LTS 2.332.3 (both inclusive) the help icon does not escape the feature name that is part of its tooltip, effectively undoing the fix for SECURITY-1955, resulting in a cross-site scripting (XSS) vulnerability exploitable by attackers with Job/Configure permission.