Using `block.timestamp` as the deadline/expiry invites MEV

code423n4 commented 7 months ago

Lines of code

Vulnerability details

Passing block.timestamp as the expiry/deadline of an operation does not mean "require immediate execution" - it means "whatever block this transaction appears in, I'm comfortable with that block's timestamp". Providing this value means that a malicious miner can hold the transaction for as long as they like (think the flashbots mempool for bundling transactions), which may be until they are able to cause the transaction to incur the maximum amount of slippage allowed by the slippage parameter, or until conditions become unfavorable enough that other orders, e.g. liquidations, are triggered. Timestamps should be chosen off-chain, and should be specified by the caller to avoid unnecessary MEV.

File: contracts/governance/twTAP.sol

307  
308          // Mint twTAP position
309          tokenId = ++mintedTWTap;
310          _safeMint(_participant, tokenId);
311  
312          uint256 expiry = block.timestamp + _duration;
313          require(expiry < type(uint56).max, "twTAP: too long");
314          // Eligibility starts NEXT week, and lasts until the week that the lock
315:         // expires. This is guaranteed to be at least one week later by the