title: Allowing users to Upload javascript/html/css
body: <p>I am creating a website which allows users to make their website alive for a certain amount of time. It works like this:</p>
  
  <ul>
  <li>user uploads a .zip file containing javascript/html/css/image.</li>
  <li>filtering the files using whitelist to remove unallowed extensions></li>
  <li>a new subdomain will be made with a random name containing the unzipped files.</li>
  <li>and the user now can view his design.</li>
  </ul>
  
  <p>so what security issues may result due uploading javascript/html/css files?</p>