[1.2.X] Fixed #14182 - documented how to modify upload handlers when using CsrfViewMiddleware

    Thus, you should always modify uploading handlers as early in your view as

    possible.

    Also, ``request.POST`` is accessed by

    :class:`~django.middleware.csrf.CsrfViewMiddleware` which is enabled by

    default. This means you will probably need to use

    :func:`~django.views.decorators.csrf.csrf_exempt` on your view to allow you

    to change the upload handlers. Assuming you do need CSRF protection, you

    will then need to use :func:`~django.views.decorators.csrf.csrf_protect` on

    the function that actually processes the request.  Note that this means that

    the handlers may start receiving the file upload before the CSRF checks have

    been done. Example code:

    .. code-block:: python

        from django.views.decorators.csrf import csrf_exempt, csrf_protect

        @csrf_exempt

        def upload_file_view(request):

            request.upload_handlers.insert(0, ProgressBarUploadHandler())

            return _upload_file_view(request)

        @csrf_protect

        def _upload_file_view(request):

            ... # Process request

Writing custom upload handlers

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