Incident Overview
On February 21, 2025, the inactive StepHeroNFTs project on BSC was exploited via a reentrancy vulnerability in the claimReferral() function, leading to a loss of approximately $90,000.
The attacker exploited a reentrancy vulnerability in the claimReferral() function, which transferred funds before updating the referral balance. By recursively calling the function, the attacker drained the contract’s assets in a single transaction before state changes could be finalized. The attacker self-referred purchases to inflate rewards and used an external call (0x2d1e) to withdraw repeatedly.
Since the victim contract was unverified, the source code was unavailable, but reverse engineering confirmed the flaw.
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 StepHeroNFTs, these are the critical security checks that could have prevented this incident (February 2025).
- Verify all logic paths related to Reentrancy are guarded by proper access controls and input validation - see the Reentrancy attack class for patterns
- Check that all state-changing functions follow the Checks-Effects-Interactions (CEI) pattern to prevent reentrancy and logic ordering bugs
- 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:
Sources & References
Learn to Prevent the Next StepHeroNFTs
The StepHeroNFTs hack is one of many attacks that skilled auditors are trained to detect before deployment. Master real exploit patterns and defense techniques with hands-on Web3 security training.