■ Description

Some tokens (e.g. LEND) revert when transfering a zero value amount.

■ Example

function transferFrom(address src, address dst, uint wad) override public returns (bool) {
        require(wad != 0, "zero-value-transfer");
        return super.transferFrom(src, dst, wad);
    }

■ How to protect against this attack?

You need to add the condition.

if(amount > 0) transfer()

■ Resources

https://github.com/d-xo/weird-erc20#revert-on-zero-value-transfers