The /etc/security/audit_user is a sensitive file and must be owned by root to prevent possible system compromise.
Change the owner of the /etc/security/audit_user file to root.
# chown root /etc/security/audit_user
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: Configuration Management.This control applies to the following type of system Unix.