Did you not get an email telling you you'd need to reset your password ?
Yes, they were "hacked" 
From the email ...
We recently became aware of some fraudulent activity on your Clubcard account, which included an attempt to access your Clubcard vouchers. We picked this up quickly and, to be on the safe side, blocked your account immediately.
This means that, when you next try to sign in, you’ll be asked to reset your password. As an extra precaution, we’ll reissue you with a new Clubcard number.
What happens now?
· All your Clubcard vouchers and points will be transferred to your new Clubcard number – rest assured you won’t lose out on any value.
· We’re working hard to give you access to your Clubcard vouchers again as quickly as possible. We estimate that this could take up to 5 working days.
· We’ll be in touch again as soon as your access is restored. You’ll then be able to see your vouchers online in your Clubcard account and on our Clubcard app.
· You can continue to collect points online (or in-store with your existing Clubcard) as normal, until your new Clubcard number is issued.
· If you’d also like a replacement Clubcard and key fobs, give us a call on 0800 591 688 to request them. They’ll take about 10 working days to arrive.
We’re sorry for any inconvenience or concern this might cause, but don’t worry – our immediate action means that nothing has been compromised. If you have any questions not answered here, please visit our FAQs here, or call 0800 591 688.
For extra tips on how to stay safe online, please visit getsafeonline.org.
Zoe Evans
UK Customer Engagement Centre