title: ExternalInterface.call works, but javascript can't access actionscript callbacks?
body: <p>In a webpage, javascript &amp; as3 are setup like this:</p>
  
  <ol>
  <li>Javascript loads the swf in the page.</li>
  <li>swf calls <code>ExternalInterface.call("javascriptFunctionName", "");</code></li>
  <li>Javascript's <code>javascriptFunctionName()</code> uses actionscript functions set up by ExternalInterface.addCallback</li>
  </ol>
  
  <p>Currently, <code>javascriptFunctionName()</code> starts by checking that it has access to the actionscript's callback functions.</p>
  
  <p>Is this check necessary? Or does the fact that the actionscript managed to call the javascript function indicate that access is granted?</p>
  
  <p>Edit: To be more specific, my code works. I'm worried that it may be put in a third party page with different permissions.</p>