AIX /etc/security/mkuser.sys.custom file must not exist unless it is needed for customizing a new user account.

The "/etc/security/mkuser.sys.custom" is called by "/etc/security/mkuser.sys" to customize the new user account when a new user is created, or a user is logging into the system without a home directory. An improper "/etc/security/mkuser.sys.custom" script increases the risk that non-privileged users may obtain elevated privileges. It must not exist unless it is needed.