title: Issue with crossorigin anonymous failing to load images
body: <p>Reference: <a href="https://stackoverflow.com/questions/33586139/prevent-http-basic-authentication-from-displaying-prompt-for-images">Prevent HTTP Basic Authentication from displaying prompt for images</a></p>
  
  <p>In order to protect my user-generated content from this potential "exploit", I added <code>crossorigin="anonymous"</code> to all <code>[img]</code> BBCodes.</p>
  
  <p>Well, it worked in IE11: when I tested the exploit, the image no longer triggered the authentication dialog (tested with cache disabled and different URLs for good measure).</p>
  
  <p>But in Chrome, the exploit doesn't work... because images aren't being loaded at all. Instead I'm getting the apparently fairly common error:</p>
  
  <blockquote>
    <p>Image from origin 'XXXXX' has been blocked from loading by Cross-Origin Resource Sharing policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'YYYYY' is therefore not allowed access.</p>
  </blockquote>
  
  <p>Maybe my understanding is wrong, but I thought the <code>"anonymous"</code> value of the attribute would allow this to work.</p>
  
  <p>Am I missing something, and if so what other options are there to protect against this issue?</p>