Another common question from Realtors is "What happens if the winning bidder backs out?"
Since online real estate auctions are legally bidding, it's not much different than a standard written purchase contract. The TERMS on a written contract spells out what happens if the buyer defaults.
You can setup the TERMS on your online real estate auction to define what is expected if the winning bidder defaults.
When a buyer defaults, it's up to you on whether you enforce the TERMS that you state.
The key is to have terms that are not too strict to scare a person from bidding, but also not too unrestricted so it isn't taken seriously.
In summary, you, as the listing agent, are in full control of what
happens when the winner bidder backs out.