title: Chrome blocking iframe requests as cross-origin request even when origins are the same
body: <p>This one has me stumped.</p>
  
  <p>I have a web app that has a file upload/download area. Files are downloaded in the background via a temporary iFrame element. This is a single-paged AJAX application and the UI is written in Javascript, jQuery and uses the jQuery.FileDownloader.js to manage the iFrame. The application runs over HTTPS and the site and download URL are on the same exact domain. The back-end is a RESTful application. This has worked great for months. Until today.</p>
  
  <p>All of a sudden, when attempting to download a file in Chrome, the browser reports an error of "Blocked a frame with origin <a href="https://example.com" rel="nofollow">https://example.com</a> from accessing a cross-origin frame."</p>
  
  <p>The problem is that the origin of the main site and that of the iframe are the exact same domain. I have ensured that the domains are the same as well as the protocol. Chrome is the only browser that throws up the cross-origin error. IE, Firefox, Opera, Safari... all work as expected. It's only in Chrome and it's only as of today. To make things worse, no updates were made to the browser. It truly is spontaneous. I've also ruled out plugins as the cause by running in Incognito mode, where none are allowed to run by my settings, as well as disabling my anti-virus software. This problem is being exhibited on other computers, in other locations (not on our LAN or subnet), all running Chrome. </p>
  
  <p>And, again, both domains of the parent frame and the embedded iframe are identical. This only happens against the production server which runs over HTTPS. Other non-HTTPS sites (e.g. our dev environment, localhost) don't have the problem. Our SSL is valid. Since this is a single-paged AJAX application, we're trying to avoid popping up another window for the download.</p>
  
  <p>Hopefully, someone can offer some advice. Thanks in advance.</p>
  
  <p><strong>Update: After additional research, I have found the solution to this problem is to enclose the filename in the response header in double-quotes.</strong></p>