CSRF fails in cross-domain iframes on IE

[Antti Kaihola]

Internet Explorer >=6
​blocks third-party cookies by default.
This ​causes CSRF to fail
for forms which are in iframes which come from a different domain. The user gets this message:

Forbidden (403)
CSRF verification failed. Request aborted.

When a developer hits this problem,
​possible solutions
are

• not use an iframe
• bring the iframed page under the same domain as the main page
• use the ​@csrf_exempt decorator for the form
• add HTTP headers to tell the browser to allow third-party cookies (see ​Chase Seibert's work around #3)

None of the solutions can be made for the developer by Django,
so the best Django can do is to provide a note about this corner case in the
​Scenarios section of the CSRF documentation.

[jedierikb@…]

A few questions about this and the proposed workarounds.

1. Could you elaborate bring the iframed page under the same domain as the main page? When using a javascript library like jQuery File Upload ​https://github.com/blueimp/jQuery-File-Upload, their javascript dynamically creates an iFrame with a form. How could the use of the library or the library itself be adjusted so as to avoid the problems described in this bug? Does it matter if the library is loaded from another site hosted elsewhere?

2. Can you pass CSRF credentials as URL parameters? This is suggested by the author of the jQuery File Upload library here ​https://github.com/blueimp/jQuery-File-Upload/pull/148#issuecomment-4251262. What are the concerns, precautions to take when doing this?

[Antti Kaihola]

Unfortunately I can't recall details of the upload functionality I was implementing when I created this ticket. I would assume that I wasn't using any JavaScript library but made a plain HTML form inside an iframe.

In this case a straightforward solution would have been getting rid of the requirement of serving the iframe contents from a separate subdomain. That's what I probably meant by "bring the iframed page..".

CSRF in query parameters would probably work. I don't seem to have thought of it back then.

[Joshua Kehn]

Will be adding documentation specific to IE >=6 and iframes.

[Mariusz Felisiak]

Microsoft deprecated all versions of Internet Explorer (see related #31032) hence we'll not describe any new IE workarounds/caveats in Django docs.