WebRTC is a free and “open project” that enables browsers and mobile applications to communicate in real time (RTC real-time communication) and to synchronize the data.
Many browsers now rely on this technology and also many website providers follow and also use these possibilities.
Which is on the one hand a very convenient thing when using many websites (you don't usually have to “save” as a rule, but rather InTime is communicated in real time between the browser and the server, but has one when used big hoes, because like in the article by Daniel Roesler's GitHub page, described in June 2015, via requests that are sent to a STUNN server, directly on VPN Communicate tunnels and find the real IP address of the user!
So if you have one now VPN Provider uses, then it may be that by using the above-mentioned browser this can lead to a problem with your anonymity.
LIVE Demo Test
This demo makes hidden requests to STUN Server that logs these queries. These queries are not shown in Developer consoles and can not be blocked by browser plugins like Adblock, Ghostery, etc.