FutureSwapX on Arbitrum was attacked, $395,000 stolen, attack method revealed

Arbitrum On-Chain Security Incident Occurs Again. According to the latest news, BlockSec detected suspicious transactions involving the FutureSwapX contract, resulting in a loss of approximately $395,000. The attacker successfully extracted USDC through carefully crafted operations. Currently, BlockSec has attempted to contact the project team but has not received a response. This incident once again reminds us that even on Ethereum Layer 2 networks, DeFi contracts face ongoing security threats.

Attack Method Analysis

Based on BlockSec’s analysis, this attack was not a traditional vulnerability exploit but was triggered through special interaction logic:

• The attacker executed multiple changePosition operations, a function typically used to adjust trading positions
• These operations cleverly influenced the contract’s internal stable balance state
• Ultimately, during position reduction or liquidation, the contract erroneously released USDC funds
• The attacker then successfully withdrew these released funds

This attack method indicates that the issue may not lie in the security of a single function but in logical flaws in contract state management.

Root Cause Still Under Investigation

BlockSec’s current analysis is preliminary. Since the FutureSwapX contract is not open source, security researchers cannot directly audit the source code and can only perform reverse engineering based on on-chain transaction behavior. Based on available information, BlockSec suspects the issue is related to the following factors:

• During early position updates, unexpected changes occurred in the stable balance
• These abnormal changes were triggered during subsequent position operations
• Ultimately, USDC was released at a time when it should not have been

However, this is only speculation based on on-chain behavior. The exact root cause requires cooperation from the project team to provide source code and detailed explanations.

Industry Insights

This incident exposes several issues worth noting:

Necessity of Contract Security Audits Even relatively simple DeFi contracts can be exploited if their logic is poorly designed. Open sourcing and third-party audits should be standard requirements.

Complexity of State Management Contracts involving multiple interacting state variables often underestimate security risks. The design of functions like changePosition requires particular caution.

Monitoring and Emergency Response BlockSec’s timely detection demonstrates the value of on-chain security monitoring, but the project’s lack of response also indicates that emergency mechanisms need improvement.

Summary

Although the scale of the FutureSwapX theft is relatively small (around $395,000), the underlying issues are quite typical: DeFi projects, in pursuit of innovative features, often embed hidden vulnerabilities in contract design details. For users, choosing projects that have undergone thorough audits, are open source, and have responsive teams remains key to reducing risk. For project teams, this incident serves as a reminder: security is not just about post-failure fixes but should be integrated throughout the entire development and deployment process.