Cache poisoning datto.com $1000 bounty

Cache poisoning is a type of cyber attack in which attackers insert fake information into a domain name system (DNS) cache or web cache for the purpose of harming users. In DNS cache poisoning or DNS spoofing, an attacker diverts traffic from a legitimate server to a malicious/dangerous server.

[dsreddy-]

Good but how you can confirm if it cached and response cache in proxy ?