Harmony Hit Hard by 4 Billion ONE Token Minting Exploit

TL;DR

• Harmony confirmed an exploit linked to roughly 4 billion unauthorized ONE tokens, equal to about 26% of the network’s pre-incident supply.
• Around 2.8 billion ONE reportedly reached exchanges quickly, while Harmony paused its bridge, deployed an emergency update and explored rollback options to contain further damage.
• ONE fell roughly 34% in one snapshot as the network faced another major security incident, with the exploit’s technical root cause still publicly undisclosed.

Harmony’s ONE token plunged after the layer-1 network confirmed an exploit connected to the unauthorized creation of roughly 4 billion tokens, an amount equal to about 26% of the pre-incident supply. The reported minting used empty blocks, while the network’s totalSupply endpoint did not immediately reflect the increase. The most unsettling detail is that billions of newly created tokens reached exchanges before Harmony could contain the damage. The project said it was working with trading platforms to freeze funds, preparing an emergency patch and evaluating whether a blockchain rollback could help address the incident.

We are working with our team and appropriate exchanges to stop and freeze the funds.

We are working on a patch and rollback options.

Will update when we have new information. https://t.co/XB0nCwTAyN

— Harmony (@harmonyprotocol) August 12, 2026

Harmony weighs rollback as billions of unauthorized ONE reach exchanges

Harmony told network operators to install an emergency software update intended to prevent further minting and paused its token bridge while investigators assessed what had happened. Four wallet addresses were identified for exchanges to block and freeze. The response now forces Harmony to balance damage control against one of blockchain’s most sensitive principles: transaction immutability. A rollback could return the chain to a state before the exploit and remove later transactions from accepted history, but that approach becomes increasingly difficult once tokens have reached exchanges or moved outside the network.

Estimates suggest approximately 2.8 billion unauthorized ONE were quickly funneled to exchanges, while about 115 million remained available to sell onchain. One account tracking the event estimated that roughly 97% of the minted amount had already reached exchanges, where it had either been sold or remained in deposit wallets. That distribution sharply limits what a rollback could realistically recover even if Harmony chooses the most aggressive response. ONE fell around 34% over 24 hours to approximately $0.0008 in one snapshot, placing the newly minted tokens’ value near $3.2 million.

The episode revives uncomfortable memories for a network that has faced serious security incidents before. Harmony’s Horizon cross-chain bridge lost nearly $100 million in 2022 after attackers compromised its multi-signature setup, an attack later attributed by the FBI to North Korean groups Lazarus and APT 38. A separate 2023 staking bug improperly created about 146.3 million ONE. The latest exploit is different because the reported damage involves unauthorized token creation directly on Harmony rather than theft from a bridge. The technical root cause remains undisclosed, leaving the network to contain funds, patch software and decide how to handle tokens already minted and distributed.