Not only enabled it but actually set an empty-string password. Usually the stored hash for a disabled account is not in the hash space, so it was either overwri

Not only enabled it but actually set an empty-string password. Usually the stored hash for a disabled account is not in the hash space, so it was either overwritten, or root account password was actually empty string out of the factory. That and the enabling of the account both point to debug code accidentally left in (or intentional backdoor by the disgruntled).