KingCZ Honeypot

Reported loss Not disclosed
BNB Chain
Honeypot

What happened

KingCZ (KCZ) is a BEP-20 token on BNB Smart Chain, deployed on 2021-05-07 at 0x40212b3f…9e0bcb. De.Fi's REKT database lists it as an exit scam/honeypot and says the contract owner could disable the transfer function, which restricted users in selling their tokens. The verified source holds a single address variable, newun, and both transfer and transferFrom revert with "please wait" for any transfer whose recipient is newun.

If newun ends up as the liquidity pair, holders cannot send tokens to the pair, which is how a swap back to BNB works. Only the owner can change newun.

How it happened

  1. The contract declares address public newun;. It is zero at deployment, so no recipient is blocked yet.
  2. transferFrom runs if(from != address(0) && newun == address(0)) newun = to;. The first transferFrom call with a non-zero from stores its recipient in newun and is allowed. The source does not name that recipient; the pair becomes newun only if the first transferFrom pays the pair, for example when a router pulls tokens from the owner to seed liquidity.
  3. After that, transferFrom takes the else branch and runs require(to != newun, "please wait");. transfer carries the same check: require(to != newun, "please wait");.
  4. A sale through a router is a transferFrom from the holder to the pair. If the pair is newun, the call reverts and the holder's balance is not changed. Transfers to any other address still work, so the token behaves normally apart from sending to newun.
  5. The owner controls the lock through function transfernewun(address _newun) public onlyOwner. Setting it to address(0) lets the next transferFrom capture a new recipient, and pointing it at an unused address lifts the block. The owner can also pass ownership with transferOwnership; the source has no function to renounce it.
  6. clearCNDAO() is onlyOwner and sends the BNB balance held by the token contract itself to the owner. It does not touch liquidity held in the pair.

Protocol details

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

Evidence

Same attack technique

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