CVE-2021-46898: Django Grappelli Open Redirect vulnerability

The vulnerability stems from the redirect URL validation logic in the switch_user view function. The original check (redirect_url.startswith('/')) was replaced with Django's secure url_has_allowed_host_and_scheme() in the patch. The function directly processes user-controlled redirect parameters and contained the flawed validation logic, making it the clear entry point for the open redirect vulnerability. The commit diff and CVE description explicitly reference this function as the vulnerable component.