The following code does not use SafeMath and can potentially lead to overflows:
While looping through all _feeReceivers it could be that a broken vault was whitelisted that allows an attacker to perform an external call and break the invariant that always 1000 tokens are left in the contract.
Add SafeMath to _sendForReceiver even though one would expect the math to be safe.
0xKiwi (NFTX) confirmed:
