False PROBLEM PLEASE DELETE

That is exactly why it is disabled by default. All that prevents access is knowing the password to the admin account. It would not be easy to guess most passwords but if someone did they could mess with your router. Mostly the risk is some bug in the software. You have exposed much more software than the NAT functionality to the outside.

Then again what can someone really do if they gain access to your router. Mostly they could open access to your internal machines so they could attempt to attack them.