title: IE11 prompts authentication window on XML HttpRequest
body: <p>I am running into an issue. The exact same request responds with 401 when sent from IE11.</p>
  <p>The endpoint to which a request is sent is a WCF service for uploading a file.
  I should probably mention that cookies are not an issue here.</p>
  <p>The following is the code that is making the request:</p>
  <pre><code>                var formData = new FormData();
                  formData.append('file', upload.file);
                  formData.append('secure_id', getCookieValue(&quot;SecureID&quot;));
  
                  var oReq = new XMLHttpRequest();
  
                  oReq.open(&quot;POST&quot;, this.fileUploadUrl, true);
  
                  var self = this;
                  oReq.onload = function (oEvent) {
                      if (oReq.status == 200) {
                          upload.status = self.$root.uploadStatusEnum.DONE;
                          upload.message = self.$root.humanFileSize(upload.file.size);
                          self.refreshData(true);
                      } else {
                          upload.status = self.$root.uploadStatusEnum.ERROR;
                          upload.message = &quot;Upload Error&quot;;
                      }
                      
                      self.processUploads(uploads.slice(0, uploads.length - 1));
                  };
                  oReq.send(formData);
  </code></pre>
  <p>IE11 left, Chrome right.</p>
  <p><a href="https://i.stack.imgur.com/2ShFm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2ShFm.png" alt="Request intercept through Fiddler. IE11 on the left. Chrome on the right" /></a></p>
  <p>I tried the following things to no avail:</p>
  <ul>
  <li>Changing XMLHttpRequest to ActiveXObject</li>
  <li>Disabling windows authentication in IIS</li>
  </ul>