Commit 147f9a0d authored by Vaclav Ehrlich's avatar Vaclav Ehrlich Committed by Tim Graham
Browse files

[1.9.x] Fixed #26201 -- Documented the consequences of rotating the CSRF token on login.

Backport of 369fa471 from master
parent 9dc22b4f
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+11 −0
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@@ -227,6 +227,9 @@ The CSRF protection is based on the following things:
   every response that has called ``django.middleware.csrf.get_token()``
   (the function used internally to retrieve the CSRF token).

   For security reasons, the value of the CSRF cookie is changed each time a
   user logs in.

2. A hidden form field with the name 'csrfmiddlewaretoken' present in all
   outgoing POST forms.  The value of this field is the value of the CSRF
   cookie.
@@ -505,3 +508,11 @@ because it invalidates all previous forms. Most users would be very unhappy to
find that opening a new tab on your site has invalidated the form they had
just spent time filling out in another tab or that a form they accessed via
the back button could not be filled out.

Why might a user encounter a CSRF validation failure after logging in?
----------------------------------------------------------------------

For security reasons, CSRF tokens are rotated each time a user logs in. Any
page with a form generated before a login will have an old, invalid CSRF token
and need to be reloaded. This might happen if a user uses the back button after
a login or if they log in in a different browser tab.