https://www.bleepingcomputer.com/news/security/ublock-origin-now-blocks-sneaky-first-party-trackers-in-firefox/

uBlock Origin on Firefox can now block first-party tracking scripts that attempt to bypass filters and rules by utilizing DNS CNAME records to load scripts from a third-party domain.

A first-party tracker is when the tracking script is located on the same domain as the web site, while a third-party tracker is when the tracking script is located on another domain.