I just saw a site called Bitundo (
http://www.bitundo.com/). It allows you to basically "undo" transactions, double spending them (sort of). What do you guys think about this, you could easily be able to exploit some sites and users easily. Example, luckyb.it pays and sends back on 0 transactions, so you could use this service to get free bets correct?
I don't know how this works, someone please explain.
It appears to work on the premise that placing another transaction with higher fees for miners should entail that transaction is included in a block before the original transaction. BitUndo have then tried to monetize the process for their own benefit.
No harm would come if used against 0-zero confirmation gambling, as the process if successful would invalidate the first/gambled transaction and also any winnings from it, since the winnings are built using an input from the first (now invalid) transaction.
