Do Proof-of-Stake (PoS) Systems Face an Equivalent to a 51 Percent Attack?

Yes, PoS systems face an equivalent threat, often termed a "51 percent stake attack" or "Long Range Attack." Instead of needing 51 percent of the hashrate, an attacker needs to control 51 percent of the total staked cryptocurrency. With this majority stake, they can gain control over block validation and finalization.

However, the dynamics differ; PoS systems are often more resistant to double-spending through mechanisms like "slashing" and "economic finality," which punish malicious validators by destroying their staked coins.