Are you asking about
FLASH? If you are looking for details regarding the project, it looks like a dead project to me.
Yes you are right, the flash project has been eradicated from the crypto space.
But Op was regarding to a situation where bitcoin can be sent with low gas fee to address A, Then once it is picked by the network, the coin exact amount is sent to address B with high priority fee, thereby leaving the first buyer (Address A) vulnerable to scam because the bitcoin will never arrive.
If you're talking about bitcoin, it's just called double spending, and the fee is just called the miner's fee (not gas).
This being said, double spending unspent outputs on the bitcoin network is not that easy. Most nodes will reject a double spending transaction as long as the original transaction is still in their mempool. Sometimes scammers use a fee that's so low the transaction never confirms, and once it's dropped from the mempool of most nodes, double spending is not that hard. Other times the scammed person is just out of luck and the double spending transaction reaches a miner before the original one does, in which case the scammer "wins".
Offcourse, opt-in RBF is also a possibility
