Harmony initiated a blockchain rollback after an Aug. 12 exploit allowed the unauthorized creation of around 4 billion ONE tokens. The mint increased the token supply by approximately 26% and sent ONE down as much as 40% in the market.
The decision means 109,126 regular transactions and 315 staking transactions recorded after the selected checkpoints will be removed. Harmony opted for a fixed rollback window after rejecting more targeted measures, citing the difficulty of distinguishing fraudulently created tokens after they had moved through exchanges, liquidity pools, and wallets.
— Harmony 💙 (@harmonyprotocol) August 17, 2026
The Rollback Removes Thousands of Blocks
Harmony set block 92,730,034 on Shard 0 and block 94,978,278 on Shard 1 as the restoration points, both corresponding to 23:25:37 UTC on Aug. 11, 2026.
Validators must install client version v2026.1.2 and use databases rebuilt from those checkpoints. This removes all blocks and transactions recorded after the checkpoints. In total, the rollback affects 141,628 blocks and more than 109,000 transactions, most of which were associated with automated activity.
The team had considered other options, including selectively burning the tokens, blacklisting addresses, replaying specific transactions, or modifying only the databases. According to Harmony, those alternatives could have created inconsistencies in the network state or accidentally affected legitimate users.
Harmony Tracks Tokens Created During the Attack
The investigation points to a single wallet that executed hundreds of transfer attempts in just over a minute. The attacker made 534 transactions of 5 billion ONE each, of which 477 succeeded, according to data released by the project.
Harmony says it has traced more than 99.9% of the related movements and is working with exchanges, cross-chain bridges, and authorities to determine where the funds went and coordinate potential recoveries.
The rollback comes after the exploit triggered heavy selling pressure on ONE. On-chain analysts had indicated that a significant portion of the newly created tokens ended up on exchanges, accelerating the impact on the token’s price.
Another Security Incident for Harmony
The incident adds to a history of security problems affecting Harmony. In June 2022, an attack on the Horizon bridge resulted in losses of approximately $100 million, while a staking bug in December 2023 allowed roughly 146.3 million ONE to be created improperly.
This time, the problem has a different dimension: it was not simply a theft of existing funds, but an unauthorized issuance capable of altering the asset’s supply.
The immediate focus is now on completing the rollback, rebuilding the network state, and coordinating reconciliation with exchanges and other infrastructure providers. The outcome will be key to determining how much legitimate activity can be recovered and whether Harmony can stabilize liquidity and confidence around ONE.
