Don't click on links you haven't requested or are from senders you don't recognise. If you have received a password reset email, we would advise for you to reset your password.
You can do that here https://www.pizzahut.co.uk/hut-rewards
Follow the steps in the email you receive. Please check your junk folder if you can't see the email. If you are using the same email and password combination for any other sites, it is advisable to change your password to a new one for those sites as well.