TacoSwap Honeypot

Reported loss Not disclosed
BNB Chain
Honeypot

What happened

TacoSwap is a BNB Chain token deployed on 31 May 2021 at 0xceae85db…5775b5 by 0x1E34aa7d…098aC9, which is still its owner. Its transferFrom stores the recipient of the first transferFrom call in a public variable, newun, and from then on both transfer and transferFrom revert with "please wait" when sending to that address. When liquidity is added through the PancakeSwap router, that first recipient is the pair, so holders can buy but every sale reverts.

The owner can reassign newun at any time with transfernewun. Only pointing it at an unused address lifts the block: clearing it re-arms the capture, so the next transferFrom, typically the next sale, stores the pair again. De.Fi's REKT database lists this TacoSwap token as a honeypot; no loss figure is recorded.

How it happened

  1. The constructor credits the deployer, who is owner, with the whole supply of 100 billion TacoSwap (0 decimals).
  2. newun starts empty. The first transferFrom runs if(from != address(0) && newun == address(0)) newun = to;. When the owner adds liquidity through the router, the router calls transferFrom(owner, pair, amount), so the pair is stored.
  3. Every later transferFrom runs require(to != newun, "please wait");. A PancakeSwap sale moves tokens from the seller to the pair with transferFrom, so it reverts with a message that suggests a temporary delay.
  4. transfer has the same check, so holders also cannot send tokens straight to the pair. Buys, where the pair sends tokens to the buyer, are unaffected.
  5. transfernewun(address) is onlyOwner and overwrites newun. Pointing it at an unused address lifts the block, and pointing it at another address moves the block there. Setting it to the zero address does not lift the block for long: the next transferFrom takes the capture branch again and stores its recipient, which after a sale is the pair.

Protocol details

Classification Token
Protocol Type Exit Scam/Honeypot
Affected asset / contract TacoSwap

Evidence

Same attack technique

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