It appears that Partial Payments Exploit, and https://xrpl.org/partial-payments.html, the flag is enabled, and once it is enabled, the partial payment transaction will be successful if it delivers any amount equal to or greater than the DeliveryMin field without exceeding the SendMax amount, or in other words :
According to the explanation, the hackers have risen
In reality, the exploiter sends over a much smaller amount specified in another transaction field and aims to receive credit for the difference.
https://cointelegraph.com/news/unknown-wallet-xrp-transfer-bitfinex-partial-payments-exploit
Can someone explain to me how it happened? I tried to understand it but I could not.