DOM-XSS for img.src

dom-xss.js

<script>
    /* In old browsers this worked: <img src=javascript:alert(1)> , tried it for DOM-XSS
       in the latest Chrome and it's not working. Any payload I can set to 
       "user_controlled_variable" to have javascript execution?

       Reference for old browsers: https://html5sec.org/#63

       .mario mentioned that it is possible to DoS firefox by setting the img.src to "javascript:while(1){}";.
          * Confirmed with latest Firefox
          * alert() calls are not allowed
          * Can't run other javascript code since it is a very restricted javascript sandbox.

     */
    ...
    el = document.createElement('img');
    el.src = user_controlled_variable;
    ...	
</script>