title: How Mega does to save a file to harddrive without requiring permission
body: <p>I'm not sure if the place to ask this question so feel free to move my question elsewhere or closed it.<br>
  I have been told that Javascript can write and read from disk only when an explicit event like drag &amp; drop happen on the browser and gave it a handle to a file.  </p>
  
  <p>In the case of Mega(ex upload) when you click download you are directly saving a file to disk without being asked to save it or installing any extension your browser.<br>
  Is it a feature of Javascript or HTML 5 because in my opinion it means a terrible security issue in this case.   </p>
  
  <p><strong>Edit 1:</strong> 
  So my question is, how do Mega manage to write on disk without showing you the <code>Save to</code> dialog of your browser popped up and self determining where to put the file</p>