Submitted by 0xsanson, also found by 0xRajeev, cmichel, defsec, GalloDaSballo, JMukesh, leastwood, loop, nikitastupin, pants, and pauliax.
Not every ERC20 token follows OpenZeppelins recommendation. Its possible (inside ERC20 standard) that a transferFrom doesnt revert upon failure but returns false.
The code doesnt check these return values. For example uToken.transferFrom(msg.sender, o.maker, a); in initiateVaultFillingZcTokenInitiate can be exploited by the msg.sender to initiate a trade without sending any underlying.
grep 'transfer' Swivel.sol
editor
Consider using OpenZeppelins library with safe versions of transfer functions.
