How to prevent Webmin users from seeing the system information, currently they are able to see system info:
Have you configured Webmin users or groups? Under Webmin\Webmin Users you can set who can see this info or use the system. I would not want general users able to access any portion of Webmin, so I would have it locked down pretty well.
If you have done this, please provide more configuration and security info about the server. Hope this helps!