Incident Overview
On Feb. 4, 2023 Sperax USD (USDs) token rebase mechanism was exploited, losing $250,000.
On February 4th, an attacker exploited the SperaxUSD protocol on Arbitrum, allowing them to increase their token balance to 9.7 billion tokens without providing matching collateral. The attacker was able to liquidate around $300k USDs before being stopped by joint actions of the Sperax team and Arbitrum ecosystem partners. The team identified the attacker's accounts on CEXs and took action against them.
All USDs transactions and the smart contract were blocked. The liquidated amount will be recapitalized by the Sperax team before relaunching the protocol. The governance token $SPA was not affected by the exploit, and USDs maintained its peg with slight fluctuations between 0.97 and 1.02 USDs/USD.
The issue has been resolved with a smart contract upgrade and recapitalization, with transactions set to restart soon.
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 Sperax USD, these are the critical security checks that could have prevented this incident (February 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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