Those running Webmin version prior to 1.330 should upgrade immediately.
Here is a quick how-to for upgrading the RPM for Redhat Linux based distros.
First check the webmin version. If you are already using 1.330, then there is no need to continue this tutorial.
rpm -q webmin
If the above command reports you are not already using version 1.330, use rpm to update your installation.
rpm -Uvh http://email@example.com/rpms/webmin-1.330-1.noarch.rpm
After it installs, please restart webmin.
service webmin restart
And thats it!
To change your root password, type the following and you will be asked for a new password.
[root@server setup]# passwd root
Good luck and may the force be with you!