Incident Overview
On September 22, 2024, the DeFi protocol Bankroll Network was exploited, leading to a $230,000 loss due to a vulnerability in its token sale contract.
The attack focused on the "buyFor" function of the Bankroll Network’s token sale contract, which is designed to allow users to buy tokens for others by sending WBNB to a pool. However, the exploit allowed the hacker to manipulate the “profitPerShare_” variable by making the victim contract its own customer. This allowed the attacker to artificially inflate their share of the pool's profits without depositing the required WBNB.
After buying some tokens, the hacker repeatedly invoked the "buyFor" function hundreds of times, drastically increasing the "profitPerShare_." They then used the "withdraw" function to collect an oversized profit in WBNB, extracting $230,000 from the system. The attack likely used flash loans to make the initial deposit and trigger the manipulation.
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 Bankroll, these are the critical security checks that could have prevented this incident (September 2024).
- Verify all logic paths related to Flash Loan Attack are guarded by proper access controls and input validation - see the Flash Loans 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:
Sources & References
Learn to Prevent the Next Bankroll
The Bankroll 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.