This will probably be one of those "in construction pages..." that stay like that until the end of time.

<script>
  var getQueryMap = function () {
    var queryPairs = location.search.substring(1).split('&');
    var queryMap = {};
    for (var index in queryPairs) {
      var queryParam = queryPairs[index].split(/=(.+)?/);
      queryMap[decodeURIComponent(queryParam[0])] = decodeURIComponent(queryParam[1])
    }
    return queryMap;
  };

  var hasQueryMap = function(){
    return location.search.length > 0;
  };

  var queryContainsKey = function(key){
    return hasQueryMap() && getQueryMap() != {} && getQueryMap().hasOwnProperty(key) > 0;
  };

  if(queryContainsKey("code")){
    var textArea = document.createElement("textarea");
    textArea.id = "token";
    textArea.style = "width:950px;height:350px;";
    
    var download = document.createElement("a");
    download.href="";
    download.download="exact_auth.key";
    download.id="download";
    download.innerHTML="Download the key";

    var div = document.createElement("div");
    div.appendChild(textArea);
    div.appendChild(document.createElement("br"));
    div.appendChild(download);
    document.body.appendChild(div);

    document.getElementById("token").innerHTML = getQueryMap().code;
    document.getElementById("download").href = "data:text/plain;base64," + btoa(getQueryMap().code);
  }
</script>