What are the risks of letting users upload and run Javascript

Question

If you have say an HTML5 games arcade, that allows users to upload a script that runs a game with HTML5 and Javascript, assuming you have no filters on their input (apart fr

Answer 1

Only my two cents..

One risk is when someone uploads a script that redirects the user to malicious website and that website is doing nasty stuff - user never intended to reach that website surely not via arcade game.