Incompatibility with tokens that charge a fee on transfer

Impact

The system stores balances in storage and then updates them

Some tokens will charge a fee on transfer

Meaning that _amount stored in the StoragePool will be higher than the actual balance received

https://github.com/blkswnStudio/ap/blob/8fab2b32b4f55efd92819bd1d0da9bed4b339e87/packages/contracts/contracts/BorrowerOperations.sol#L841-L851

  function _poolAddColl(
    address _borrower,
    IStoragePool _pool,
    address _collAddress,
    uint _amount,
    PoolType _poolType
  ) internal {
    _pool.addValue(_collAddress, true, _poolType, _amount);
    IERC20(_collAddress).transferFrom(_borrower, address(_pool), _amount); /// @audit FOT / SafeTransfer
  }

These types of tokens are pretty rare, but this is a very common finding that you should think about

Mitigation

Imo acknowledge this and make sure not to use these tokens

GalloDaSballo / Apollon-Review

Incompatibility with tokens that charge a fee on transfer #35

Impact

Mitigation