[jeroenhd]

You can disable WebRTC in most decent browsers if you're afraid this will be abused. WebRTC can be used for worse things (like port scanning your internal network) and for great things (video calling with millisecond latency, Peertube).

However, it should be noted that this mechanism doesn't just allow remote sockets to be created through Javascript. It can only communicate with other servers that either use some version of WebRTC/WebSockets or plaintext services that ignore the extra protocol overhead as garbage and happily parse the rest (some IRC servers and WebSockets are a nice example).

As you can see in the technical overview, people use peer to peer technology to connect to your browser, which then uses WebSockets to communicate with a WebSocket server for a normal Tor entry point.