RFC8482 – Saying Goodbye to Any

While an “ANY” query has somewhat defined semantics on the DNS authoritative side, it’s undefined on the DNS resolver side. RFC8482 specifies that:

This clearly defines the corner case – from now on the authoritative server may respond with, well, any query type to an “ANY” query. This makes us more confident the resolver isn’t used to perform DNS reflections:

On the client side, just don’t use ANY DNS queries.

Source: blog.cloudflare.com