In Django 1.11.x before 1.11.18, 2.0.x before 2.0.10, and 2.1.x before 2.1.5, an Improper Neutralization of Special Elements in Output Used by a Downstream Component issue exists in django.views.defaults.page_not_found(), leading to content spoofing (in a 404 error page) if a user fails to recognize that a crafted URL has malicious content.
https://www.djangoproject.com/weblog/2019/jan/04/security-releases/
https://www.debian.org/security/2019/dsa-4363
https://usn.ubuntu.com/3851-1/
https://lists.debian.org/debian-lts-announce/2019/01/msg00005.html
https://groups.google.com/forum/#%21topic/django-announce/VYU7xQQTEPQ