Beedle - Oracle free perpetual lending

Summary

Because Front-running is a key aspect of AMM design, deadline is a useful tool to ensure that your tx cannot be “saved for later”.
Due to the removal of the check, it may be more profitable for a miner to deny the transaction from being mined until the transaction incurs the maximum amount of slippage.

Vulnerability Details

Most of the functions that interact with AMM pools do not have a deadline parameter, but specifically the one shown below is passing block.timestamp to a pool, which means that whenever the miner decides to include the txn in a block, it will be valid at that time, since block.timestamp will be the current timestamp.

Impact

A malicious miner can hold the transaction, which may be being done in order to free up capital to ensure that there are funds available to do operations to prevent a liquidation. It is highly likely that a liquidation is more profitable for a miner to mine, with its associated follow-on transactions, than to allow the decrease of liquidity. A miner can also just hold it until maximum slippage is incurred, as the judge stated.

Tools Used

Manual review

Recommendations

Add deadline arguments to all functions that interact with AMMs and pass it along to AMM calls.