The ... attack essentially realizes that the hash cannot be reversed; rather than trying to find out what the password is, the attacker just sends over the hash. If the attacker can obtain a

The ... attack essentially realizes that the hash cannot be reversed; rather than trying to find out what the password is, the attacker just sends over the hash. If the attacker can obtain a valid username and user password hashes values (just the hash—the attacker does not know the actual password), then the hacker can use that hash, without ever knowing the actual password.