Note the “flood and loot” paper is explicitly pointed out in the full disclosure mail post with a discussion of the lightning security model, where spending a HTLC output with a preimage on the outgoing link after the timelock on the incoming HTLC has expired is deemed as illegitimate.

Note, how the issue sounds to generalize to any “revoked” or “invalid” state in off-chain bitcoin protocols, where an attacker might be able to replace cycling package out of the mempool (assuming package relay support and deployment).

theariard

bitcoin

[bitcoin-dev] Full Disclosure: CVE-2023-40231 / CVE-2023-40232 / CVE-2023-40233

Rsync25

You really have to explain this stuff better.

The way I would answer that question is to say that the party with the preimage does have the right to spend the output. But in this circumstance, they're deliberately delaying that spend long enough that the HTLC in the channel sending the funds times out first. In _that_ circumstance spending the HTLC output with the preimage is no longer legitimate, as the node in the middle didn't get their money.