Currently, Firefox only has DoH rolled out in the US, so CloudFlare is in that same jurisdiction. Additionally, all DoH providers included in Firefox must meet

Currently, Firefox only has DoH rolled out in the US, so CloudFlare is in that same jurisdiction. Additionally, all DoH providers included in Firefox must meet the Trusted Recursive Resolver (TRR) guidelines, sign a contract to that effect, and undergo third-party audits to ensure they meet the requirements. https://wiki.mozilla.org/Security/DOH-resolver-policy https://wiki.mozilla.org/Security/DOH-resolver-policy This is all publicly documented. As Mozilla rolls DoH out to other regions they will add additional TRR partners and CloudFlare won't be the only choice.