If you visit a site that exploits the WebRTC vulnerability including whatismyipaddress.com it may show "Local IP Address" which would be the real IP of your machine.
The vulnerability works on Windows and Linux machines (contrary to false information on the web which claims it only affects Windows).
The above works and happens even if you are using a proxy or VPNaccount like ProVPNAccounts.com
It is easy........
So you've just purchased your SSL cert, renewed it and installed it or maybe you've had it installed and working fine all the time with all other browsers but you've upgraded to a recent version of Firefox and suddenly get the warning "Error code: sec_error_unknown_issuer" error.
This is terrible since if you bought an SSL cert, you are most likely using it for trust purposes for your business and obviously that message will scare away most potential customers.........