According to Fab Distribution Agreement, Seller already agrees and Accept responsibility and Liability for their Content and Ensure all rights belongs to them.
However, According to Fab EULA, I case of any Damage caused by use of Asset, Nor Epic nor Seller is Responsible (Kind of Strange but for Epic Protection).
Although, my recommendation would be to Look out for Sellers who Brand their Product well with for example, you would find their Name anywhere (From marketing Materials, In Products, They may have their own Domain) those kind of Sellers are Safe Bet (although No Guarantee) since they are Promoting their name as well with Product, They won’t do anything wrong Intentionally since it will ruin their Name and Reputation. Although lot of Sellers doesn’t do that but it is my method to Filter Safest Bet Especially for Non Generic Content like Vehicles, Characters, etc.