[MAVEN:GHSA-92MR-4W2Q-4578] Exposure of Sensitive Information to an Unauthorized Actor 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.