A simple program that will let you connect to any IP and modify parameters of the client's avatar.
Download and extract the .zip file from releases and run VrcOscParameterController.exe
Here you can put in either your your local or public IP address.
Local: Using 127.0.0.1 should work, as well as inputting your direct IPV4 address. This will only let you control parameters on your local machine.
Public: If you have a port-forwarded IP address or an application like LogMeIn Hamachi, you can use those addresses. So if your friend had yours, they can put it into the program and mofify YOUR avatar parameters since it's your address.