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........
A few days ago this happened on multiple Centos 5 servers and apparently anyone using rpmforge was affected by this error and there was no solution other than disabling that repo to fix it.
To some this highlighted a few points, that there is a reason RHELexists with full paid support, and also that this could be a vulnerability and huge flaw with yum. A yum search or install should not segfault just because the rpmforge repo goes down.
Fortunately it came back up........