Harmony plans blockchain rollback following 4 billion ONE token exploit

The Harmony ONE blockchain is undergoing a major recovery process following a massive exploit that resulted in the unauthorized minting of approximately 4 billion ONE tokens. Onchain researchers reported that the attacker created these forged tokens through empty blocks, representing roughly 26% of the previously reported supply. An estimated 2.8 billion tokens were moved quickly toward exchanges.

In response, Harmony has issued an emergency validator patch and paused its bridge. The network has announced plans to perform a blockchain rollback to a checkpoint recorded at 11:25 pm UTC on August 11. This decision will discard more than 109,000 regular transactions and 315 staking transactions. Harmony stated that selectively restoring transactions was deemed unsafe due to potential discrepancies in balances, contract states, and nonces on the replacement chain.

The exploit appears to target Harmony’s native cross-shard accounting and legacy consensus verification code. Investigators have traced nearly all forged tokens to specific wallets or service boundaries and are currently working with law enforcement, bridges, and exchanges to manage the fallout.