This is a brand new scam.
What happens is someone issues you a refund, they use this information to create FAKE transactions in your paypal account. Here is the screenshot of the "refund".
They then hit your account with LOADS of purchases for games / CD Keys,
etc.
Here is a screenshot of my fake transactions.
You should check your account (Log in yourself by typing in www.paypal.com - Do not trust links.)