BlockDev Sp. Z o.o: Steal ALL collateral during liquidation by exploiting lack of validation in `flip.kick`

Summary: The flip contract allows for the MCD system to auction collateral in exchange for DAI. A lack of validation in the method flip.kick allows an attacker to create an auction with a fake bid value. Since the end contract trusts that value, it can be exploited to issue any amount of free DAI...