According to the faq http://groupon.my/faq

Does Groupon store my credit card information?
No, we dont. Groupon does not have access to your credit card details at all. While it seems like it is stored in your account, it is actually placed in the highly secure Adyen electronic vault. This is to ease the purchasing process for you, so that shopping on Groupon would be convenient.

Does Groupon have access to our credit card details?
At no point would any Groupon staff (or even Adyen staff) has access to your credit card details - it is highly encrypted and locked from view, just like the payment details for millions of other Groupon customers around the world. The only information available to us to view would be the type of card (Visa or Master) - something to help us identify the type of card you use in order to ease refunds, if any.

I am still uncomfortable with my credit card info being stored - whether with Groupon or with your payment gateway. What can I do?
While we try to move towards global standards, we totally understand how some customers may not prefer to have their payment method saved in the system - and would prefer paying the manual way instead. If this is something you wish, you could always write to us with your account email address to request a permanent removal. We will immediately disable your accounts feature to keep your credit card details.

We still think its not right to store the credit card info, especially if its a 3rd party provider. Could you provide us some screenshots to look into this further?