Unlock Protocol Hack

TOTAL LOST $38K
Low Other

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain 2023 Incident surface
Recovered - No recovery reported
All-Time Rank #1780 By amount stolen
Auditors 1 Prior security audit

Incident Overview

Quick Summary

On the 21th of April we has detected a security breach aimed at UnlockProtocol that resulted in a significant loss of more than 20 ETH.

Details of the Exploit

The root cause of this breach is related to the "postLockUpgrade()" function in the implementation contract 0xdcb2f7d1…fd6b93, which failed to verify the caller.

During the preparation phase of the attack, the attacker called the "postLockUpgrade()" function in transaction 0x4ac413c3…033ef6. The purpose of this function call was to set the "locks[].deployed" parameter to True, allowing the attacker to pass the "onlyFromDeployedLock()" check on the "recordKeyPurchase()" function in the subsequent transaction.

It should be noted that an accomplice address, 0x3a683332…0e3c0e, was used to deposit 16 ETH into Tornado. The attacker used this address to obfuscate their tracks and make it more difficult to track the flow of funds.

Block Data Reference

Exploiter contract:

https://etherscan.io/address/0xac08f1af…152e84

Exploiter:

https://etherscan.io/address/0x43ee4169…57bb71

Incident Report

Protocol / Project Unlock Protocol
Date of Incident
Attack Technique Other
Classification NFT
Primary Source View Post-Mortem

Protocol Information

Protocol Type Payments
Affected Token UDT
Official Website unlock-protocol.com/
Protocol Twitter/X @UnlockProtocol
Team Anonymous
Source Code Unverified

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.

Technical Knowledge Deep understanding of other and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in Unlock Protocol's contract logic - root cause: nft
Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block
Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Other audit checklist and test coverage
Audited by Code4rena — still lost $38K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to Unlock Protocol, these are the critical security checks that could have prevented this incident (April 2023).

  • 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

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

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Security Audit History

Sources & References

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