Jenkins before versions 2.44, 2.32.2 uses AES ECB block cipher mode without IV for encrypting secrets which makes Jenkins and the stored secrets vulnerable to unnecessary risks (SECURITY-304).
https://jenkins.io/security/advisory/2017-02-01/
https://github.com/jenkinsci/jenkins/commit/e6aa166246d1734f4798a9e31f78842f4c85c28b