This demo secretly makes requests to STUN servers that can log your request. These requests do not show up in developer consoles and cannot be blocked by browser plugins (AdBlock, Ghostery, etc.).
Additionally, these STUN requests are made outside of the normal XMLHttpRequest procedure, so they are not visible in the developer console or able to be blocked by plugins such as AdBlockPlus or Ghostery. This makes these types of requests available for online tracking if an advertiser sets up a STUN server with a wildcard domain.