CVE-2018-17144 (Bitcoin Optech)

Bitcoin Optech's index entry on CVE-2018-17144, a 2018 Bitcoin Core bug that could have allowed an inflation or double-spend under specific conditions. It was responsibly disclosed, patched quickly, and — by available evidence — never exploited on mainnet before nodes upgraded.

It appears in this topic as a precedent for handling a latent, high-severity flaw without a live attacker forcing the timeline. That is a meaningfully easier case than a quantum threat, where the "attacker" capability could arrive gradually and ambiguously rather than as a single disclosed bug.