Hello Pablinni,
This message means, that your device is accessible from the internet. Meaning that anyone can connect to it.
It is caused by some open ports on your device.
Since you recently updated to Win 10, it is most likely port 80 on your computer. Win 10 have sometimes IIS (web server) enabled and running by default.
Guide on how to uninstall IIS (if you are not hosting any websites on your PC, you don't need it):
https://technet.microsoft.com/en-us/library/cc779925(v=ws.10).aspxThe message is saying, that your router is accessible from outside, but is displayed on your PC. Not on your router in the Network Scan results.
This is a mistake on Avast's side. It should be saying "your PC" not "your router".
We will fix the message to be more accurate.
Thank you for reporting this,
Filip