Incident Overview
On April 15, 2025, a compromised admin account exploited the ZKsync airdrop distribution contracts and stole approximately $5 million worth of unclaimed ZK tokens.
The attack stemmed from the compromise of the admin address 0x842822...587D, which had privileged access to three airdrop distribution contracts. Using this access, the attacker called the sweepUnclaimed() function and minted around 111 million unclaimed ZK tokens, representing roughly 0.45% of the total token supply. This unauthorized minting directly inflated the circulating supply and resulted in the attacker gaining control of tokens worth about $5 million.
Importantly, this was an isolated incident affecting only the airdrop contracts; the ZKsync protocol itself, the core ZK token contract, governance contracts, and capped minters were not compromised. The attacker still holds most of the stolen funds at 0xb1027e...05d3, and recovery efforts are ongoing in coordination with Seal and various exchanges. The ZKsync team has reached out to the attacker to encourage communication and possible fund return.
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 ZKsync, these are the critical security checks that could have prevented this incident (April 2025).
- Verify all logic paths related to Private Key Compromised (Unknown Method) / Access Control are guarded by proper access controls and input validation - see the Access Control Attacks attack class for patterns
- Review privileged functions (owner, admin, governance) for potential abuse vectors - centralization risks should be documented and bounded with timelocks or multi-sigs
Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.
Free TrialRelated Attack Classes
The technique used in this hack maps to these vulnerability classes in our security curriculum:
Proof-of-Concept Exploits
On-Chain Evidence & References
Sources & References
- 01
- 02
- 03
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