We have a rule setup to give free shipping on orders over $49. We had a very suspicious order come through where the discount didn't make sense:
You can see in the screenshot the only coupon listed in savings is the "eligible for free shipping". Yet they got $150 listed here. If you look at the product rows they got a hefty discount for each item in the order.
This person paid with the standard magento paypal module.
Here's our Shopping Cart Price Rule config:
So it it a misconfig or exploit?