Cloudfare July 2019 Incident: Regex's exponential runtime

A Cloudflare outage from 2019 has roots in regex change done in WAF (Web Application Firewall). Exponential runtime regex match caused outages.

The incident is described in the excellet “Post Mortem” blog post by Cloudflare : https://blog.cloudflare.com/details-of-the-cloudflare-outage-on-july-2-2019/

References:

Explained in this excellent video by Kevin Fang: https://www.youtube.com/watch?v=DDe-S3uef2w