Cross-site scripting (XSS) vulnerability in the render_full function in debug/tbtools.py in the debugger in Pallets Werkzeug before 0.11.11 (as used in Pallets Flask and other products) allows remote attackers to inject arbitrary web script or HTML via a field that contains an exception message.
https://lists.debian.org/debian-lts-announce/2017/11/msg00037.html
https://github.com/pallets/werkzeug/pull/1001
http://blog.neargle.com/2016/09/21/flask-src-review-get-a-xss-from-debuger/