title: How to filter filetypes in plupload's HTML5 runtime?
body: <p>I'm integrating plupload with my ASP.NET MVC3 application, with the following settings:</p>
  
  <pre><code>var uploaderSettings = {
      runtimes: "html5,silverlight,flash,html4",
      browse_button: "browse-button",
      container: "upload-ui",
      drop_element: "drag-drop-area",
      file_data_name: "file",
      multiple_queues: true,
      max_file_size: "10mb",
      url: '@Url.Action("Index", "Upload")',
      flash_swf_url: '@Url.Content("~/js/plupload/plupload.flash.swf")',
      silverlight_xap_url: '@Url.Content("~/js/plupload.silverlight.xap")',
      filters: [
          {title: "Excel Files", extensions: "xls,xslx,csv"}
      ],
      multipart: true,
      urlstream_upload: true,
      dragdrop: true,
      multipart_params: {
          token: "@AuthToken()"
      }
  };
  </code></pre>
  
  <p>From which plupload is generating an <code>&lt;input type="file"&gt;</code> with the following items in the <code>accept</code> attribute (comma separated):</p>
  
  <ul>
  <li><code>application/vnd.ms-excel</code></li>
  <li><code>application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</code></li>
  <li><code>text/csv</code></li>
  </ul>
  
  <p>In Firefox 12.0, it ignores the filter and allows selection of any filetype.</p>
  
  <p>In Chrome 21, it doesn't work with the file extensions mentioned, but if I change the filter to image files (jpg, png, gif) it filters the Choose File dialog correctly.</p>
  
  <p>I found <a href="http://code.google.com/p/chromium/issues/detail?id=54009" rel="nofollow">this issue</a> on the Chromium bug tracker, which seems to be related, but was marked as fixed back in October 2010.</p>
  
  <p>If I switch the runtime priority to silverlight or flash above html5, it works correctly, but I'd rather not do this as I lose the drag and drop file upload functionality.</p>
  
  <p>Is this simply the limitation of browser support for the accept attribute, am I doing something wrong, or is it a bug in plupload?</p>
  
  <p><strong>UPDATE:</strong> it appears this is a <a href="https://github.com/moxiecode/plupload/issues/526" rel="nofollow">known issue</a>, and boils down to browser support for mime-type filtering.</p>