Bitcoin's BIP-54 proposal aims to fix a serious vulnerability known as "attack blocks." Maliciously constructed transactions may require nodes to spend an extremely long time to verify. This issue was first discovered in 2013, and it exploited the quadratic expansion characteristic of signature hash (sighash) operations in inputs before (SegWit), which could cause severe network latency or denial-of-service attacks. The soft fork solution proposed by this proposal sets a new consensus limit on the total number of CHECKSIG and CHECKMULTISIG operations per transaction in non-SegWit inputs at 2500, thereby dramatically reducing potential verification time from several minutes to fractions of a second, and mitigating a critical barrier to network scalability.