The Harmony blockchain has suffered a major security exploit that resulted in the fraudulent minting of approximately 4 billion ONE tokens, equivalent to roughly 26% of the cryptocurrency's total supply. The attack exploited a vulnerability tied to empty blocks and triggered rapid movement of the newly created tokens across hundreds of wallets. The incident is Harmony's second major security breach, following a separate $100 million hack of its Horizon Bridge in June 2022. Unlike that earlier attack, which targeted the cross-chain bridge connecting Harmony to other networks, this exploit appears to stem from a vulnerability in the blockchain's core block-processing logic.

The scale of the exploit has raised serious concerns about the impact on existing ONE holders, market stability, and the integrity of the blockchain's transaction history. More than 10,000 transfers involving the fraudulently minted tokens were traced across 409 wallets. Of those tokens, approximately 2.8 billion were reportedly transferred to cryptocurrency exchanges, contributing to a sharp decline in the price of ONE, which dropped by as much as 50%.

Harmony responded by deploying an emergency software patch, instructing validators to upgrade, pausing its bridge service, and coordinating with exchanges to freeze funds linked to the exploit.

Harmony Traces Funds and Alerts Exchanges

Harmony stated that its investigation identified 10,288 transfers involving the affected tokens distributed across 409 wallets. The project also notified exchange partners about hundreds of suspicious deposit transactions associated with the stolen funds.

According to Harmony, exchange partners responded by blocking and freezing the identified hacker-controlled wallets. The team provided exchanges with information linking the suspicious funds to four wallet addresses believed to be connected to the exploit.

This effort is intended to prevent the fraudulently created ONE tokens from being converted into other assets or withdrawn from trading platforms while the blockchain team determines how to address the underlying damage.

Harmony also paused its bridge service, bridge.harmony.one, following the incident. The measure was intended to reduce the possibility of further movement of affected assets during the emergency response.

Emergency Patch Targets Minting Vulnerability

Harmony released an emergency software update designated v2026.1.1 and instructed validators to upgrade their nodes. The patch was designed to prevent the vulnerability from being exploited to create additional tokens.

We are asking all exchanges to block and freeze funds that traces back to these 4 wallet addresses:

one1uap8dx2z0qsjxqthm5flgcxkeepsz3gsrghnfn

0xe7427699427821230177dd13f460d6ce43014510

one17u300a40ll5wphd8kj5hktryhdjq3ml9f4phy4

0xf722f7f6afffe8e0dda7b4a97b2c64bb6408efe5…

— Harmony (@harmonyprotocol) August 12, 2026

The blockchain project reported that 53% of its validators had completed the upgrade approximately four hours after the emergency patch was released. Harmony thanked validators and other participants for supporting the rapid response while continuing to work on measures addressing the tokens that had already been minted.

The distinction between stopping additional minting and resolving the existing supply increase remains significant. While the patch can prevent the same vulnerability from generating more tokens, it does not automatically remove the billions of ONE already created through the exploit.

Rollback Could Reshape Recent Transactions

Harmony indicated that a blockchain rollback had emerged as the most practical solution under consideration. Such a move could potentially remove fraudulent transactions from the chain and restore the ledger to a state prior to the exploit. The most prominent historical precedent for this approach is the Ethereum community's 2016 hard fork following the DAO hack, which reversed exploitative transactions but also resulted in the chain splitting into two separate blockchains — Ethereum and Ethereum Classic — after a faction of users continued the original, unmodified chain.

Due to the incident, we have paused .

— Harmony (@harmonyprotocol) August 12, 2026

However, a rollback could create complications for legitimate users. Transactions involving the affected tokens may have passed through exchanges or other wallets before the funds were identified. Reversing blockchain activity could therefore affect users who acquired the assets without knowing they were connected to the exploit.

All validators, please upgrade. This patch prevents any further minting. We'll follow up with another update to address the already minted tokens.

— Harmony (@harmonyprotocol) August 12, 2026

At the same time, leaving the fraudulent tokens in circulation could substantially dilute existing holders, as the unauthorized minting increased the effective supply by billions of ONE.

The rollback decision therefore represents a major trade-off: removing fraudulent activity could restore the intended token supply, while reversing transactions may also affect legitimate users who interacted with the blockchain after the exploit.

We traced 10288 transfers across all 409 wallets where the fraudulently minted tokens have landed, and alerted exchange partners on hundreds of suspicious deposit transactions. They promptly blocked the hacker's wallets. As of now, 53% of our validators completed the upgrade…

— Harmony (@harmonyprotocol) August 12, 2026

Harmony has stated it will provide additional details after evaluating the available options. Until a final resolution is reached, the project is relying on validator upgrades, exchange-level fund freezes, and the suspension of its bridge to contain the incident.

The exploit highlights the continuing security risks faced by blockchain networks, where a vulnerability affecting transaction processing or block validation can have immediate consequences for token supply, market prices, and user funds. The incident also underscores the importance of rapid coordination among blockchain developers, validators, and cryptocurrency exchanges when responding to large-scale security breaches.

With the emergency patch now preventing further fraudulent minting, Harmony's next major challenge is determining how to handle the approximately 4 billion previously created ONE tokens without causing unnecessary disruption to legitimate users.