Incident Overview
On June 4, 2026, the BYToken contract on the BNB Chain was exploited for approximately $87,400 (146.6 BNB) via a flash-loan price manipulation attack.
The attack capitalized on an unprivileged, public function named triggerAutoBurn() inside the BYToken contract. The exploiter initiated the attack by securing a massive flash loan of roughly 422,000 WBNB from Moolah (Lista DAO). Using a portion of these funds, they executed Initial swaps to set up the pool conditions, then called the public triggerAutoBurn() function.
This function was designed to reduce token supply but lacked proper caller access controls, allowing the attacker to force a massive burn of ~67.8 quadrillion BY tokens directly from the BY/WBNB PancakeSwap pair. Following the burn, the contract triggered a pool sync(), which recalculated the token reserves down to a near-zero level while keeping the WBNB amount high. This extreme imbalance massively skewed the token price formula ($x \cdot y = k$).
The attacker exploited this artificial premium by selling a minimal amount of BY back into the pool, draining the remaining WBNB liquidity before repaying the flash loan.
Exploit tx: https://bscscan.com/tx/0xe31c681e…980979
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 BYToken, these are the critical security checks that could have prevented this incident (June 2026).
- Verify all logic paths related to Flash Loan Attack 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
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