“If you’re using an ad blocker, there’s a 99.99% chance you are using EasyList or one of its derivatives.”
The filter list behind nearly every ad blocker is a text file run by volunteers. An abandoned Android browser, forked into apps popular in India, downloads it on every startup. Traffic jumped 10 to 20 times, Cloudflare throttled it and said serving it may break the terms of service. The whole ad-blocking business runs on a free file that one buggy fork can knock over.