Submitted by rotcivegaf, also found by 0x4non, 0xDecorativePineapple, 9svR6w, adriro, ajtra, aviggiano, brgltd, carlitox477, chaduke, codexploder, corerouter, joestakey, ladboy233, s3cunda, saian, Trust, V_B, and wait
Exchange.sol#L212-L227
The Yul call return value on function _returnDust is not checked, which could leads to the sender lose funds
The caller of the functions bulkExecute and execute could be a contract who may not implement the fallback or receive functions or reject the call, when a call to it with value sent in the function _returnDust, it will revert, thus it would fail to receive the dust ether
Proof: 
nonfungible47 (Blur) confirmed and commented:
