===========================
Django 1.4.18 release notes
===========================

*Under development*

Django 1.4.18 fixes several security issues in 1.4.17 as well as a regression
on Python 2.5 in the 1.4.17 release.

WSGI header spoofing via underscore/dash conflation
===================================================

When HTTP headers are placed into the WSGI environ, they are normalized by
converting to uppercase, converting all dashes to underscores, and prepending
`HTTP_`. For instance, a header ``X-Auth-User`` would become
``HTTP_X_AUTH_USER`` in the WSGI environ (and thus also in Django's
``request.META`` dictionary).

Unfortunately, this means that the WSGI environ cannot distinguish between
headers containing dashes and headers containing underscores: ``X-Auth-User``
and ``X-Auth_User`` both become ``HTTP_X_AUTH_USER``. This means that if a
header is used in a security-sensitive way (for instance, passing
authentication information along from a front-end proxy), even if the proxy
carefully strips any incoming value for ``X-Auth-User``, an attacker may be
able to provide an ``X-Auth_User`` header (with underscore) and bypass this
protection.

In order to prevent such attacks, both Nginx and Apache 2.4+ strip all headers
containing underscores from incoming requests by default. Django's built-in
development server now does the same. Django's development server is not
recommended for production use, but matching the behavior of common production
servers reduces the surface area for behavior changes during deployment.

Bugfixes
========

* To maintain compatibility with Python 2.5, Django's vendored version of six,
  :mod:`django.utils.six`, has been downgraded to 1.8.0 which is the last
  version to support Python 2.5.