Django 1.1.4 release notes
- Backwards incompatible changes
  - CSRF exception for AJAX requests

Django 1.1.4 release notes

Welcome to Django 1.1.4!

This is the fourth “bugfix” release in the Django 1.1 series, improving the stability and performance of the Django 1.1 codebase.

With one exception, Django 1.1.4 maintains backwards compatibility with Django 1.1.3. It also contains a number of fixes and other improvements. Django 1.1.4 is a recommended upgrade for any development or deployment currently using or targeting Django 1.1.

For full details on the new features, backwards incompatibilities, and deprecated features in the 1.1 branch, see the Django 1.1 release notes.

Backwards incompatible changes

CSRF exception for AJAX requests

Django includes a CSRF-protection mechanism, which makes use of a token inserted into outgoing forms. Middleware then checks for the token’s presence on form submission, and validates it.

Prior to Django 1.2.5, our CSRF protection made an exception for AJAX requests, on the following basis:

Many AJAX toolkits add an X-Requested-With header when using XMLHttpRequest.
Browsers have strict same-origin policies regarding XMLHttpRequest.
In the context of a browser, the only way that a custom header of this nature can be added is with XMLHttpRequest.

Therefore, for ease of use, we did not apply CSRF checks to requests that appeared to be AJAX on the basis of the X-Requested-With header. The Ruby on Rails web framework had a similar exemption.

Recently, engineers at Google made members of the Ruby on Rails development team aware of a combination of browser plugins and redirects which can allow an attacker to provide custom HTTP headers on a request to any website. This can allow a forged request to appear to be an AJAX request, thereby defeating CSRF protection which trusts the same-origin nature of AJAX requests.

Michael Koziarski of the Rails team brought this to our attention, and we were able to produce a proof-of-concept demonstrating the same vulnerability in Django’s CSRF handling.

To remedy this, Django will now apply full CSRF validation to all requests, regardless of apparent AJAX origin. This is technically backwards-incompatible, but the security risks have been judged to outweigh the compatibility concerns in this case.

Additionally, Django will now accept the CSRF token in the custom HTTP header X-CSRFTOKEN, as well as in the form submission itself, for ease of use with popular JavaScript toolkits which allow insertion of custom headers into all AJAX requests.

Please see the CSRF docs for example jQuery code that demonstrates this technique, ensuring that you are looking at the documentation for your version of Django, as the exact code necessary is different for some older versions of Django.