FASTSWAP Hack

TOTAL LOST $291K
Low Other

Summarize with AI

ChatGPT Perplexity Claude Grok
Affected Chain 2021 Incident surface
Recovered - No recovery reported
All-Time Rank #1158 By amount stolen
Auditors 1 Prior security audit

Incident Overview

The attacker:

https://bscscan.com/address/0xfd544b21…fd0921, as was stated by the project team in the tweet:

https://archive.is/4MRMN

tokenMigrate() function was called by the address which probably was saved to MasterChef in the constructor() initialization into private variable migrateAddress. Since the caller of the tokenMigrate() function was address 0x193D4D22…8D15ef, he was able to invoke LP and token migrations multiple times at:

https://explorer.bitquery.io/ru/bsc/txs/calls?contract=0xad4219cd…64d701&method=99594431

After, tokens were transferred to the external address multiple times, the example transaction:

https://bscscan.com/tx/0x5bb2d2ce…b0f9e2

Liquidity was removed multiple times, tokens were sold as well, the example transaction:

https://bscscan.com/tx/0x830f9f79…b144ba

Incident Report

Protocol / Project FASTSWAP
Date of Incident
Attack Technique Other
Classification Exchange (DEX)
Primary Source View Post-Mortem

Protocol Information

Protocol Type Dexs
Affected Token FAST, Duke
Official Website fastswap.finance/#/
Protocol Twitter/X @fastswapdex

Market Context at Time of Hack

Token Categories
MultiversX Ecosystem
Protocol Links
GitHub Discord

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 FASTSWAP's contract logic - root cause: exchange (dex)
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 $291K. Prior audits don't guarantee safety, especially after post-audit code changes.

If you're auditing a protocol with similar architecture to FASTSWAP, these are the critical security checks that could have prevented this incident (August 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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