I got curious and looked up both IPs associated with the domain name and it is in fact just CloudFlare
also, their DNS-over-HTTPS (this is new to me but I stay the fuck away from cloudflare and it looks like a standard they’ve pushed for) endpoint is just the 1.1.1.1 one with the domain name changed, but the AdGuard and Accelerator ones basically confirm they’re analyzing traffic before passing it off to cloudflare
see I don’t have a smoking gun on this, but if it is a garden variety adblocker and whatever the accelerator does (it’s extremely unclear) running on cloudflare workers, they at least have the ability to MiTM and modify DNS queries, and open proxies are always a security nightmare. my impression is the filter list they link is either what that endpoint uses to filter, or it’s LLM vomit they kept in because it felt more legitimate.
this might be worth poking at more in a controlled setting — a command line DNS-over-HTTP client using their endpoints and some exploration of the open proxy with curl (especially with sites that utilize credentials, with great care taken to use disposable accounts for this) might be illuminating