The following flaw was found in Jenkins:

The re-key admin monitor was introduced in Jenkins 1.498 and re-encrypted all secrets in JENKINS_HOME with a new key. It also created a backup directory with all old secrets, and the key used to encrypt them. These backups were world-readable and not removed afterwards.

Jenkins now deletes the backup directory, if present. Upgrading from before 1.498 will no longer create a backup directory. Administrators relying on file access permissions in their manually created backups are advised to check them for the directory $JENKINS_HOME/jenkins.security.RekeySecretAdminMonitor/backups, and delete it if present.

All administrative monitors now require the user accessing them to be an administrator.

External References:

https://wiki.jenkins-ci.org/display/SECURITY/Jenkins+Security+Advisory+2017-02-01

Upstream patch:

https://github.com/jenkinsci/jenkins/commit/0be33cf7328fad6a7596ce9505a74561a8b1eb85