[1.7.x] Fixed #22310 -- Documented exact usage of SECRET_KEY

    security protections, and can lead to privilege escalation and remote code

    execution vulnerabilities.

The secret key is used for:

* All :doc:`sessions </topics/http/sessions>` if you are using

  any other session backend than ``"django.contrib.sessions.backends.cache"``,

  or if you use

  :class:`~django.contrib.auth.middleware.SessionAuthenticationMiddleware`

  and are using the default

  :meth:`~django.contrib.auth.models.AbstractBaseUser.get_session_auth_hash()`.

* All :doc:`messages </ref/contrib/messages>` if you are using

  :class:`~django.contrib.messages.storage.cookie.CookieStorage` or

  :class:`~django.contrib.messages.storage.fallback.FallbackStorage`.

* :doc:`Form wizard </ref/contrib/formtools/form-wizard>` progress when using

  cookie storage with

  :class:`django.contrib.formtools.wizard.views.CookieWizardView`.

* All :func:`~django.contrib.auth.views.password_reset` tokens.

* All in progress :doc:`form previews </ref/contrib/formtools/form-preview>`.

* Any usage of :doc:`cryptographic signing </topics/signing>`, unless a

  different key is provided.

If you rotate your secret key, all of the above will be invalidated.

Secret keys are not used for passwords of users and key rotation will not

affect them.

.. setting:: SECURE_PROXY_SSL_HEADER

SECURE_PROXY_SSL_HEADER