In Django 1.10.x before 1.10.8 and 1.11.x before 1.11.5, HTML autoescaping was disabled in a portion of the template for the technical 500 debug page. Given the right circumstances, this allowed a cross-site scripting attack. This vulnerability shouldn't affect most production sites since you shouldn't run with "DEBUG = True" (which makes this page accessible) in your production settings.
https://www.djangoproject.com/weblog/2017/sep/05/security-releases/
https://usn.ubuntu.com/3559-1/