I double-checked, and in my opinion this backdoor is fully intentional.
He checks if the cookie called "remember" exists, but that cookie is not set anywhere.
This means that the script expects that a human will set that cookie manually, because manually setting it is the only way it can exist.
The intention was not to take advantage of a backdoor. Instead it was a silly mistake meant to give the option for the admin to not have to relogin everytime.
It has already been fixed and can be checked by faucet owner on the script.As I mentioned in the first post this has been done as a hobby and service is meant to be free. You can now check that it has been fixed.
Thank you for bringing this up. My intention is to make honest business and help new faucet creators.