An extremely critical vulnerability has recently been discovered in WebRTC (Web Real-Time Communication), an open-source standard that enables the browsers to make voice or video calls without needing any plug-ins. The security glitch affects browsers such as Google Chrome and Mozilla Firefox, and appears to be limited to Windows operating system only, although users of Linux and Mac OS X are not affected by this vulnerability. Luckily the critical security flaw is quite easy to fix. The only extensions that block these look ups are JavaScript blocking extensions such as NoScript.
Source: https://thehackernews.com/2015/02/webrtc-leaks-vpn-ip-address.html