Jack's mother told the BBC she had left her password for the eBay auction site in her computer and her son used the "buy it now" option to complete the purchase.
"Jack's a whizz on the PC and just pressed all the right buttons," Rachel Neal said.
The seller of the second-hand car, a dealer from Worcestershire, central England, was amused by the bid and agreed not to force the sale through.
"Luckily he saw the funny side and said he would re-advertise," Neal said.
What do you think? If you were the owner, would YOU have done the same thing or would you have forced the woman to pay for the car?