Incident Overview
On August 12, 2026, Layer-1 blockchain Harmony Protocol suffered a major protocol-level security incident when an attacker exploited an "empty blocks" vulnerability to fraudulently mint approximately 4 billion ONE tokens representing roughly 26% of the token's total circulating supply and causing the price of ONE to crash between 26% and 34%.
The exploit targeted a consensus or state-update bug involving empty blocks, allowing the attacker to mint ~4 billion ONE tokens out of thin air while bypassing standard protocol reporting endpoints (leaving totalSupply metrics temporarily unchanged). The attacker rapidly transferred approximately 2.8 billion ONE (~97% of the fraudulently created tokens) directly into centralized crypto exchanges for liquidation, leaving only around 115 million ONE in on-chain addresses. In response, Harmony requested exchanges to freeze funds from four identified attacker wallet addresses while the core team began developing a software patch and evaluating blockchain rollback options.
Key Attacker Addresses:
one1uap8dx2z0qsjxqthm5flgcxkeepsz3gsrghnfn (0xe7427699…014510)
one17u300a40ll5wphd8kj5hktryhdjq3ml9f4phy4
Incident Report
Protocol Information
What the Attacker Needed to Succeed
Understanding the prerequisites for this type of attack helps auditors identify protocols that are most at risk and helps developers build better defenses.
What Auditors Should Check
If you're auditing a protocol with similar architecture to Harmony, these are the critical security checks that could have prevented this incident (August 2026).
- Verify all logic paths related to Other are guarded by proper access controls and input validation
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
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