jenkins before versions 2.44, 2.32.2 is vulnerable to a user creation CSRF using GET by admins. While this user record was only retained until restart in most cases, administrators' web browsers could be manipulated to create a large number of user records (SECURITY-406).
https://jenkins.io/security/advisory/2017-02-01/
https://github.com/jenkinsci/jenkins/commit/b88b20ec473200db35d0a0d29dcf192069106601