Harmony Protocol moves to reverse downtrend with rollback plan announcement

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Harmony has published a detailed rollback plan that would rewind its blockchain to cancel the effects of an attacker who forged billions of ONE tokens.

The move will discard every transaction confirmed on the network since the incident, deleting legitimate user activity along with the fraud.

What is Harmony doing to its blockchain?

The Harmony network has announced that it will return to the state it was in on August 11, 2026, at 23:25:37 UTC. All transactions that happened after that date and time, including the fake ONE tokens that were created by a hacker, as well as any legal buys, sells, or transfers that users made, will be erased.

The company chose this specific time because the first fake tokens appeared in the very next block on Shard 0, which was block number 92,730,036.

The block just before it, number 92,730,034 (Shard 1) was never attacked, but it is being rolled back at the same time to prevent any future problems. The network will then start creating new blocks from heights 92,730,035 and 94,978,279.

Harmony’s new client software, v2026.1.2, will refuse to accept the block hashes tied to the hack. 

Before the team decided on a fixed rollback window, a targeted burn to destroy the fake token was considered as an initial solution. However, the fake ONE tokens had already been sent to exchanges, trading pools, and smart contracts; burning them could have accidentally taken money that belongs to innocent people.

The company also rejected the idea of a blacklist, because that would leave the fake supply in the system, and selectively replaying transactions was called “unworkable” because the state of the chain has changed. The idea of a full token migration was also rejected because it would have caused too much disruption for all users.

Simply using a built-in revert tool to move the chain head was also warned against, as this could leave behind unwanted data that might lead to another failure.

Harmony Network’s report states that an independent security firm reviewed the hack and agreed with the rollback solution.

How did the hack happen?

The hack was first noticed by on-chain expert “Juiceberg,” who estimated that the attacker used a flaw in how the network checks cross-shard receipts to process the same receipt more than once, creating tokens out of thin air.

After the attack was made public, the price of the ONE token fell, and it is currently around $0.0007.

Roughly 4 billion ONE, about 26% of the token’s supply, had been conjured through empty blocks.

Harmony says it is now investigating where the money went. The hacker tried to send 534 payments of 5 billion tokens each in just 106 seconds. Of those, 477 payments went through, moving a huge amount of 2,385,000,000,000 ONE.

The team tracked the flow of money and found that most of the fake tokens ended up in a wallet or reached a service like an exchange. Harmony says it is now working with exchanges, crypto bridges, and police to keep records and find the criminals.

Cryptopolitan reported that Harmony had a similar problem in December 2023, when a bug in its staking system created 146.28 million ONE tokens by accident, forcing the company to update its network.

Separately, Harmony’s Horizon bridge lost about $100 million in a June 2022 theft that the FBI attributed to North Korea’s Lazarus Group.

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