That's not the fault of Cars.com. That's a scam. There are scams on Craigslist, and Autotrader and even eBay, as well.
Cars.com functions much like Autotrader. A person or dealership selling a vehicle/vehicles pays and posts a listing with details about the vehicle and transaction. The person then posts contact information for you, the buyer, to contact them directly.
When I was looking for my car, I saw MANY MANY cars posted online that "looked great" but had suspicious information. In this day and age, you have to be very very careful who you're dealing with. I would NEVER buy anything for more than $1000 that I can't see first hand before paying for it.