The SVCB HTTPS rfc considers downgrade attacks here: https://www.rfc-editor.org/info/rfc9460/#name-handling-resolution-failure https://www.rfc-editor.org/info/r

The SVCB HTTPS rfc considers downgrade attacks here: https://www.rfc-editor.org/info/rfc9460/#name-handling-resolution-failure https://www.rfc-editor.org/info/rfc9460/#name-handling-resol... And essentially boils it down to ‘either the client implements wire-security to a known dns server using DoH or DoT, implements dnssec to verify the untrusted response as legitimate, or the client risks being mitm’d to attacker addresses’. They ultimately sidestepped the problem by structuring it to be hints rather than guarantees and thus allowing DNSSEC to be optional, and so as of today, it’s definitely not sufficient to implement this. I think that adding a CORS rejection to DNS — declaring subdomains independent of a TLD, that is — does not require DNSSEC, so long as clients adhere to the steps to prohibit attacker interference described. But it still asks a great deal of DNS that I’m unsure is possible today, not just in DNSSEC but in ripple-subward records that somehow tie into client responses. More likely, I assume browsers will simply permanently end all service to the concept of subdomains at all; no cookie sharing across domains at all, no inherent cross-origin just because tld and www.tld share a few characters, etc. rather than either depending on the PSL or having to implement strange and complex DNS anything. Admins will throw their hands up about it, but the net is no longer a place where control of a TLD defines the trust of its subordinates, so it’s certainly time to rip that bandaid off if they haven’t yet.