Ethereum co-founder Vitalik Buterin emphasized the core security feature of blockchains, stating that even in the event of a 51% attack, invalid blocks cannot be made valid, preventing validators from stealing user assets. However, Buterin warned that this security does not extend to off-chain trust scenarios. In such cases, if 51% of validators collude to provide incorrect results, users would have no recourse, as these situations fall outside the blockchain's control.