M^0: Malicious minters can repeatedly penalize their undercollateralized accounts in a short peroid of time, which can result in disfunctioning of critical protocol functions, such as `mintM`.

M^0's MinterGateway allows minters to call updateCollateral() and, whenever they are undercollateralized, applies a compounding penalty proportional to the shortfall on each call. Because the penalty grows principalOfActiveOwedM each time, a malicious minter w …