There's been an increase in the number of domains using CNAMEs to try and mask tracking - essentially allowing trackers to masquerade as 1st party rather than 3rd party sites.
Adguard have released a list of underlying CNAMEs - https://github.com/AdguardTeam/cname-trackers/tree/master/trackers
- however they're not in a particularly convenient format so will need some processing for inclusion.
They're of (relatively) limited use in browser-based adblocker extensions (only those that use dns.resolve
or similar will see the CNAME target to block it), but are of use in Pihole and various other DNS based solutions.