Earlier this month a few members of Groupon started reporting unapproved activity on their accounts. Apparently hundreds of pounds have gone missing too! In fact there are reports that members have been out of pocket by upto £1000. It's not overly clear how the hackers obtained these details and Groupon state that there has not been a security breach on their Website or mobile app.
You'll want to check your accounts and update passwords ect... Also check your bank to make sure that you're safe.