Submitted by jonah1005, also found by 0xRajeev, shw, JMukesh, and cmichel
A non standard ERC20 token would always raise error when calling _safeTransferFrom.  If a user creates a USDT/DAI pool and deposit into the pool he would find out theres never a counterpart deposit. See TransferHelper.sol #L19.
TransferHelper does not uses SafeERC20 library as the function name implies.
A sample POC:
Error Message:
Recommend using openzeppelin SafeERC20 in transferHelper (and any other contract that uses IERC20).
talegift (Wild Credit) confirmed
ghoul-sol (Judge) commented:
