title: Catching async exceptions from CORS request
body: <p>I'm letting users upload files to an amazon s3 bucket by granting them signed URL's from a web server via an ajax call.</p>
  
  <p>Every once and a while the request will go haywire and give me a 403 (As to why I don't know). I have try catch blocks wrapped around my xhr request, but this exception doesn't get caught.</p>
  
  <p>Looks something like this</p>
  
  <blockquote>
    <p><a href="https://bucket.s3.amazonaws.com/hB22C1m9KAll477LWIGx42fTuK4htm?AWSAccess" rel="nofollow">https://bucket.s3.amazonaws.com/hB22C1m9KAll477LWIGx42fTuK4htm?AWSAccess</a>…JKQ6DXF43A&amp;Expires=1385394844&amp;Signature=/OKomeLHinfcDvm30O/9b+9edkw=
    403 (Forbidden)
    bucket.s3.amazonaws.com/hB22C1m9KQ6DXF4TuK4htm?AWSAccessKeyId=AK…Q62CNKF3PC3QLA&amp;Expires=1385394844&amp;Signature=/OKomeLHkplfcDvm30O/9b+9edkw=:1</p>
  </blockquote>
  
  <p>So 2 questions.</p>
  
  <ul>
  <li>Is it possible to catch an async exceptions from a CORS requests?</li>
  <li>Why would I be getting a forbidden? (Only thing I can think of is if the URL expired, but I have a long timeout, and it gets used the moment it's received from the server via AJAX).</li>
  </ul>