What happens if someone outbids me right as the auction is about to end?

On The Block protects against this practice (commonly known as 'sniping'). Auctions are extended automatically by at least 5 minutes when any last minute bid is placed, allowing other participants the chance to increase their bids should they wish. This soft close will continue for any new bids made until 5 minutes have passed with no bidding.

This is NOT LIKE EBAY, the quickest click will not win a property if other bidders want to improve their offer(s). There is always an opportunity for individuals to make their best offer because the clock will continue to extend until all bidders have allowed the timer to reach 0. It is for this reason that it is not advisable to wait until the last second of an auction, as there is no benefit to try to be the last bidder.