Firefox's integration with Cloudflare for DNS-over-HTTPS
"By default, Firefox ships with support for relaying encrypted DoH requests via Cloudflare's DoH resolver, but users can change it to any DoH resolver they want"
Mozilla is obviously working more and more in direction to integrate everything with big tech surveillance companies. Perhaps it is high time to reconsider Tor Browser being based on some other browser rather than being a patch-work of some anti-privacy software like Firefox. Perhaps a good start may be ungoogled-chromium (which makes zero background connections to anything by default).