According to @Excellion, the greatest danger can come from well-funded, well-intentioned developers optimizing Bitcoin Core validation, citing PR #9049 which aimed to speed initial pre-relay block validation by removing a duplicatable duplicate-input check that screens blocks before network relay; this highlights risk in code paths that touch consensus-critical verification. source: @Excellion PR #9049, titled "Remove duplicatable duplicate-input check from CheckTransaction," describes skipping a costly duplicate-input check during initial pre-relay processing to accelerate block validation, altering how nodes initially vet incoming blocks prior to relay. source: Bitcoin Core GitHub PR #9049 Security-critical validation changes have historically required urgent patches when flaws were found, such as the 2018 consensus vulnerability CVE-2018-17144 that led to immediate upgrades in Bitcoin Core 0.16.3, underscoring why market participants track such proposals as operational risk events for BTC exposure. source: Bitcoin Core 0.16.3 release notes; MITRE CVE-2018-17144