On April 15, a hacker exploited a compromised admin account tied to ZKsync’s airdrop contracts. The attacker was able to mint 111 million unclaimed ZK tokens worth $5 million using a function known as sweepUnclaimed(). This led to an increase in the total token supply by 0.45%, but it did not affect any user funds. ZKsync disclosed the incident promptly and confirmed that the attack was isolated, emphasizing that no other systems or assets were compromised during the attack.
Following the attack, ZKsync began working closely with the Security Alliance (SEAL) to recover the stolen funds. The compromised account had administrative control over three airdrop distribution contracts, which were exploited to mint the unclaimed tokens. ZKsync assured users that the sweepUnclaimed() function was no longer a threat and that its governance and token contracts were not affected. These actions prevent further exploits through the same vulnerability, giving the community confidence in the platform’s resilience.
ZKsync operates as an Ethereum layer-2 protocol, processing main-layer transactions with the help of zero-knowledge rollups.
At the time of the attack, the platform’s total value locked was $57.3 million. ZKsync had also been working on an airdrop of 17.5% of its token supply to participants in the ecosystem. Despite the security breach, the protocol’s core functionality remains intact, and ZKsync has assured users that no further vulnerabilities exist through this vector.
The attack caused significant volatility in the price of ZKsync’s ZK token. Within an hour of the hack’s disclosure, the token’s value dropped by 16%, though it later rebounded slightly, recovering to $0.047. Over the next 24 hours, the ZK token still saw a 7% decrease in value. This hack is part of a larger trend in the cryptocurrency world, where $2 billion has been lost to hacks in the first quarter of 2025 alone, highlighting the increasing risks within the sector.
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