This topic is related to basic signature so recommended to be moved.

Thanks. Not sure how to foward the rest of the conversation to the referred beginer topic/thread. Ok, my understandig is that the digital signature is to confirm the ownership of the Private Key but not to the remaining data of the transaction. I would appreciate if you can clarify further as to how signature also covers the remaining data besides the Private Key or pass any relevant link(s). Thanks.

What prevents a fraudster to divert the pending payment? Here is the scenario:

Step-1: User-1 initiates TXN-1 for payment to User-2 and the TXN is not yet confirmed i.e. POW is ongoing.
Step-2: A fraudster( someone listening or participating in the NW),  in the meantime while POW is pending, creates a new TXN-2 to pay the funds to User-3 by copying the rest of the TXN-1 data including the input Signature/Script.
Step-3: if miners reject both TXN-1 & TXN-2 suspecting that it is a double spend, what prevents the fraudster to issue a new TXN-3 by copying the TXN-2( if needed changing the payment to User-4) for the next block POW or confirmation?

In other words, the question boils down to copying the input script/signature from pending transaction for fraud.
Thanks in advance.