WebRTC stands for Web Real Time Communication. It's used for most web related voice, video, or file sharing capabilities. Specifically instances of communication where you are directly connecting to your peer through your browser. Some examples could be web-games that let you play tic-tac-toe with a friend. Sharing files directly through a browser to another peer. Most browsers have native support for WebRTC except for Internet Explorer and Safari. It uses encryption for all its communications, but as you've found there's a huge vulnerability.
It seems that Windows and FreeBSD are the vulnerable operating systems. I'm currently running a Debian based distro, and it does not seem to be vulnerable based on the two links you've provided.
It does not appear that you can only block the leaked IP vulnerability and use WebRTC for its intended use.
Mitigations
I'm not sure which plugin you've installed to disable WebRTC. This article states that both WebRTC Block and ScriptSafe extensions for Chrome will stop the vulnerability. For Chrome make sure that all Chrome processes have been closed after you've installed the extension. Sometimes the Chrome sandboxes aren't properly closed when the browser window is. This will ensure the new extension has taken effect properly.
For FireFox the NoScript add-on should block the request. You can also disable some settings with the following steps:
- Type
about:config
in the address bar
- Find the setting
media.peerconnection.enabled
and set it to false
- Find the setting
media.navigator.enabled
and set it to false
I would not suggest using Internet Explorer as a mitigation... a leaked IP would probably be the least of your worries. Switching OSs is an option, but probably a tedious one.