Get the Crypto Payment Security & Compliance Playbook
Back to Blog

BonqDAO Exploited on Polygon: $120M Stolen Due to Flawed Logic

Code Auditing
February 2, 2023
5 min read

On February 2nd, 2023, BonqDAO on Polygon was attacked, resulting in losses of approximately 98.6M BEUR and 113M WALBT. After investigation, we found that the flawed logic used to determine the WALBT token price was the cause of the attack. As a blockchain security company, we closely monitor such exploits that can have far-reaching implications in the DeFi space.

Date Attack type Chain Lost Recovered
2023/2/1 Flawed Price Dependency Polygon ~ $120 M No

Project Introduction

BonqDAO (Bonq Decentralized Autonomous Organization) is a DeFi lending platform deployed on Polygon. Users can provide liquidity to the protocol or take out overcollateralized loans to earn yields, and then they can mint BEUR, a stablecoin pegged to the Euro.

After this attack, BonqDAO's TVL plummeted from $13 million to $44,000, experiencing a 99.66% decline.

BonqDAO subsequently announced that the Bonq protocol had been suspended, and AllianceBlock and the Bonq team minted new ALBT tokens and airdropped them to affected users.

Attack Analysis

TellorFlex is the Oracle of BonqDAO. It is decentralized and anyone can become a price provider by staking only 10 TRB tokens and modify the oracle price at will.

The attacker carried out profits in two ways during this attack:

  • Raise the WALBT's price and then borrow a massive amount of BEUR tokens
  • Lower the WALBT's price and then liquidate other use’s WALBT.

The attacker's strategy can be broken down into the following key steps:

  1. Prepare funds
  2. The attacker staked a 10 TRB tokens and increased the price of WALBT tokens through TellorPriceFeed (0x8f55).
  1. The attacker then deposits 0.1 WALBT and directly uses the updated price to obtain 100M BEUR.
  1. The attacker used the same method to manipulate WALBT to drop to a low price, liquidate other BonqDAO users’ WALBT collateral, and then resell them for further profit.

Fund Tracking

As a company dedicated to maintaining blockchain security, we have also been closely monitoring the progress of this attack. (Our official Twitter account has been continuously reporting on this incident, and interested readers can follow our account @BlockSecTeam@MetaSleuth to track the movement of these funds together.)

MetaSleuth is a high-performance cross-chain fund flow analytics tool that enhances the transparency of blockchain transaction activity. It allows users to nearly real-time track the trail of affected digital assets. By leveraging MetaSleuth, we can clearly see the relevant fund flow tracking information during the occurrence and follow-up of this attack.

  1. The profit of the BonqDAO attacker was approximately 98.6M BEUR and 113M WALBT. Specifically, 113M WALBT was burned to unlock 113M ALBT from the ETH chain. Approximately 0.5M BEUR was swapped for 534,535 USDC and then swapped for Ethereum (0xcacf...6642). The attacker still had 98.1M BEUR remaining in their Polygon account.
  1. Regarding the Ethereum address 0xcacf..6642 , it used 0xExchange(@0xproject ) to swap the received USDC for DAI. Additionally, WALBT is swapping into ETH/USDT using 0xExchange and Uniswap. The account currently holds 711 ETH, 534,481 DAI, and 89M ALBT.
  1. On Feb 3, 2023, we detected that the attacker had swapped DAI for Ether and laundered 1,105 Ether via Tornado Cash.

Summary

The root cause of this attack is that the cost of collateral required for modifying the quotation of TellorFlex oracle is too low, and the amount of collateral borrowing in the Bonq lending contract is only related to the price reported by TellorFlex oracle. Therefore, attackers can modify the quotation at a relatively low cost and get considerable profits through collateral borrowing.

Read More

The above are just representative cases. In fact, we have more cases focusing on blockchain security analysis.

DeFi Exploit Analysis: The Root Cause of Euler's $200M Loss

About BlockSec

BlockSec offers a full stack security service for blockchain projects, providing assistance from pre-launch to post-launch and incident response. During the development and testing stages, Expert Code Auditing Services and the Phalcon fork testing platform are employed to help identify potential security issues. Ensure robust post-launch security for your blockchain project with BlockSec Phalcon. This streamlined SaaS platform offers incident alerts and automatic blocking to prevent crypto hacks. It employs precise attack detection, scanning both pending and on-chain transactions, allowing you to swiftly intercept hackers. Additionally, MetaSleuth is an intuitive crypto tracking and investigation platform that helps enhance the traceability and transparency of assets.

Sign up for the latest updates
Web3 Attack Surfaces: A Penetration Testing Overview
Security Services

Web3 Attack Surfaces: A Penetration Testing Overview

Crypto institutions keep every traditional attack surface and add the money-handling chain on top of it. This article gives testers a practical abstraction of the running system: a four-component model—Application, Authorization and Signing, Blockchain Interaction, and Infrastructure—with each component's responsibility, representative implementations, and inherited attack surfaces. It then structures web3-specific coverage into five attack-surface areas, from production and automation operations through signing intent, approval and withdrawal chains, and fund logic to on-chain transactions and deployed contracts.

~$23M Lost: Cosmos EVM, Moonwell Exploits | BlockSec Weekly
Security Insights

~$23M Lost: Cosmos EVM, Moonwell Exploits | BlockSec Weekly

During the reporting period (2026/08/22 - 2026/08/30), we cover 5 blockchain security incidents totaling approximately $22.7M in losses; an estimated $74M-$119.5M was drained from Tectonic, most of it erased when Cronos was rolled back to its pre-exploit state. The highlight is a six-chain Cosmos EVM exploit series (~$5.7M realized), traced on TAC Chain, where a shared balance-synchronization bug chained an underflow and an overflow to drain a staking pool. The report also analyzes Moonwell's combined collateral-accounting and oracle price manipulation, Tectonic's combined oracle-price and receipt-token exchange-rate manipulation of low-liquidity collateral, an Ajna liquidation business-logic flaw, and a Rain Card Contract Exploit Series with an Ed25519 signature-verification bypass (Avici, Tria, and others) on Solana.

Rules of Engagement and Production Safety for Institutional Blockchain Penetration Testing
Security Services

Rules of Engagement and Production Safety for Institutional Blockchain Penetration Testing

A penetration test that touches signing, withdrawal, and ledger systems is prepared before it runs. This article follows the engagement lifecycle: turning a business decision into objective, scope, named owners, and authorized access; recording authority, permitted techniques, operating limits, prohibited activity, communications, and evidence handling in a Rules of Engagement document; and protecting live service with measurable stop criteria, monitoring, change coordination, and named pause authority. It closes with the remediation and retest that turn findings into validated controls.

Best Security Auditor for Web3

Validate design, code, and business logic before launch. Aligned with the highest industry security standards.

BlockSec Audit