Harmony Proposes Rollback To Resolve Hack That Forged Trillions of Tokens

The team said it traced the forged tokens to blocks created just after 23:25UTC on 11 Aug, when the exploit began. It proposed reverting every block produced after that point, restoring the chain to its pre-exploit state but also discarding 109,126 regular transactions and 315 staking transactions confirmed in the meantime. Harmony's analysis, published on X, showed that 96% of the affected transactions were automated, with decentralized exchange bots accounting for 99,863 of them.

Early estimates valued the forged tokens at roughly $3.2mn at post-crash prices, but that figure may not represent the total financial damage from the exploit as Harmony reconciles differing calculations of how many ONE tokens were forged.

Harmony is a Layer 1 blockchain designed to host decentralized finance (DeFi) applications, while using separate shards to process transactions in parallel. The network uses its ONE token for staking, transaction fees and participation in its proof-of-stake system.  The exploit adds to a growing list of security failures affecting DeFi infrastructure in 2026, even as traditional financial firms increasingly explore bringing assets and services onchain. TRM Labs recorded 207 crypto hacks in the first half of the year, more than double the 83 recorded a year earlier, with losses estimated at $972mn. 

Unresolved amount forged

Following the discovery of the exploit, Harmony said in an X post that the attacker had exploited a flaw in the way the network verified transfers. Transfer records could be replayed, allowing the same transfer to be credited multiple times without the corresponding amount being debited. The process resulted in additional ONE tokens appearing in otherwise empty blocks.

Harmony published two estimates for the amount of ONE forged and said it was "currently reconciling two different impact measurements." The first, 4bn ONE, reflected what the team described as the initial wave of unauthorized issuance, attributed to two block credits and equivalent to about 25% of the token's existing supply. A broader accounting of the exploit, however, put total forged issuance at just over 3tn ONE across six transactions sent to four wallets.

Soon after identifying the exploit, Harmony deployed an emergency fix that prevented further unauthorized minting. 

The plan for rollback

Following the patch to fix the vulnerability, a rollback was deemed as the best solution to return the token issuance back to its authorized amount. A simple rewind of the existing databases was ruled out because it would leave fragments of the discarded period behind, which could reopen the attack or leave validators running different versions of the chain.

Instead, the chain will be rolled back to a point shortly before the exploit began, providing an additional margin of safety, and then rebuilt using replacement blocks prepared by the team. The forgery affected only one of Harmony's two shards, parallel chains that process activity separately, but both will be rolled back to the same point to keep them synchronized.

The team said it examined similar recovery decisions on blockchain networks including Bitcoin, Ethereum and BNB Chain, as well as Nasdaq's reversal of erroneous trades, before settling on a single fixed rollback window. It said the approach applies one rule to everyone while minimizing the risk of another exploit or a validator split. According to the Harmony X post, an independent security firm that reviewed the incident reached the same conclusion.

Frosty reaction

The plan sets no date, saying only that it will be carried out once validator agreement, exchange alignment and technical conditions are met. Holders replying to the teams post asked what happens to ONE tokens staked on exchanges, which the plan does not address. One called the investment "the biggest mistake I have made in crypto."

After the plan is carried out, Harmony's team will have to convince its token holders to trust the project going forward. Since the attack was identified on 12 Aug, the ONE token price has dropped by 41% according to CoinGecko data. The token has remained below the one-cent mark since late Sept 2025, with a market capitalization of about $11mn as of 18:08UTC on 17 Aug.