xWin Finance Hack

TOTAL LOST $270K
Low Other

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain 2021 Incident surface
Recovered - No recovery reported
All-Time Rank #1183 By amount stolen
Auditors 1 Prior security audit

Incident Overview

The attacker's address:

https://bscscan.com/address/0xb63f0d8b…c2ad19

The transaction behind the attack:

https://bscscan.com/tx/0xba0fa8c1…c05c1d

The attacker:

- flash loaned 76,000 BNB from Fortube Bank

- swapped 37999.99 BNB for 95.409 xWin tokens via PancakeSwap V1 BNB+xWin Pool due to an invalid slippage control in the xWinFundP::_swapBNBToTokens() function

- deposited 37999.99 BNB and 0.003 xWin tokens into PancakeSwap V1 BNB+xWin Pool as liquidity and minted in return 11.28 PancakeSwap LP tokens. Got an extra amount of xWin tokens as a reward from xWin Finance

- swapped 95.406 xWin tokens for 75995.77 BNB via the above PancakeSwap V1 BNB+xWin Pool and burnt 11.28 PancakeSwap V1 LP tokens to get 4.19 BNB

- repeated one to four twenty times, the attacker got about an extra 303,998.86 xWin tokens reward from xWin Finance for this attack

- swapped 303,998.86 xWin tokens for 903.92 BNB via PancakeSwap V2 BNB+xWin Pool and returned the flash loan in the first step

607,998 xWin tokens were transferred to the attacker, and then it was used to swap for BNB. This incident was due to a bug in the internal _swapBNBToTokens() function of the xWinFund contract which implements a price slippage control.

Incident Report

Protocol / Project xWin Finance
Date of Incident
Attack Technique Other
Classification Yield Aggregator
Primary Source View Post-Mortem #1 View Post-Mortem #2

Protocol Information

Protocol Type Indexes
Affected Token XWIN
Official Website xwin.finance/
Protocol Twitter/X @xwinfinance
Team Anonymous
Source Code Unverified

Market Context at Time of Hack

Token Categories
BNB Chain Ecosystem
Protocol Links
GitHub

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.

Technical Knowledge Deep understanding of other and Solidity and EVM internals
Capital Required Seed capital to cover gas and initial position setup
On-Chain Access Ability to interact with smart contracts and deploy a custom exploit contract
Protocol Analysis Identification of the exploitable vulnerability in xWin Finance's contract logic - root cause: yield aggregator
Execution Speed Precise transaction ordering and timing to exploit the vulnerability within a single atomic block
Obfuscation Plan A strategy to launder and move stolen funds - typically through mixers, cross-chain bridges, or decentralized DEX swaps to resist tracing

What Auditors Should Check

Could this have been caught in audit? Likely — with a thorough Other audit checklist and test coverage
Audited by Audit Report 1 — still lost $270K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to xWin Finance, these are the critical security checks that could have prevented this incident (June 2021).

  • Verify all logic paths related to Other 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

Master these auditing techniques with hands-on labs and real exploit scenarios in the Smart Contract Hacking course.

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Security Audit History

Sources & References

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