An upstream patch has been backported to fix a security vulnerability in python-django. CVE-2019-3498: Content spoofing possibility in the default 404 page
An attacker could craft a malicious URL that could make spoofed content appear on the default page generated by the django.views.defaults.pagenotfound() view. The URL path is no longer displayed in the default 404 template and the request_path context variable is now quoted to fix the issue for custom templates that use the path.