# M^0 Minter Gateway audit Three Sigma · Stablecoin framework · 8th January 2024 A private security review of M^0 (stablecoin framework), conducted with Three Sigma and completed on 8th January 2024. 0xSimao disclosed 32 findings: 3 high severity, 3 medium, 9 low and 17 informational. ## What M^0 is M^0 is a neutral value-transmission framework: permissioned minters generate $M against eligible off-chain collateral, validators attest collateral values on a cadence, and a two-token governance system (the TTG) sets every parameter, aiming at digital money with the risk profile of physical cash. ## Scope The Three Sigma review covered the minter gateway and governance: collateral update signatures and their timestamps, the penalty regime for missed intervals, mint proposals and delays, and the invariants tying total principal to outstanding owed M. ## High severity findings - [Lack of deadline in PowerToken.buy can lead to user's cashToken being distributed through ZeroToken holders](https://0xsimao.com/findings/m-0-deadline-cash-through-zero) - [Validator signature with zero timestamp can always be replayed](https://0xsimao.com/findings/m-0-signature-zero-timestamp-replayed) - [MToken's total principal invariant can be broken](https://0xsimao.com/findings/m-0-total-principal-invariant-broken) ## Medium severity findings - [Creating a new proposal in StandardGovernor may reach a state of permanent DoS](https://0xsimao.com/findings/m-0-creating-proposal-reach-permanent) - [A sufficiently large collateral may break the maximum owed M calculation](https://0xsimao.com/findings/m-0-sufficiently-collateral-maximum-owed) - [Validator signatures with greater timestamps can be reused in a subsequent updateCollateral](https://0xsimao.com/findings/m-0-greater-timestamps-subsequent-collateral) ## Low severity findings - [Multiplication after division in StableEarnerRateModel leads to loss of precision](https://0xsimao.com/findings/m-0-stable-earner-model-precision) - [A decrease in updateCollateralInterval will lead to unfair penalties](https://0xsimao.com/findings/m-0-collateral-interval-unfair-penalties) - [Unhandled rounding error in DistributionVault.getClaimable leads to locked dust](https://0xsimao.com/findings/m-0-rounding-claimable-locked-dust) - [MToken's total principal invariant doesn't hold without MinterGateway, leading to potential principal loss](https://0xsimao.com/findings/m-0-invariant-hold-minter-gateway) - [Unrealized inflation calculation returns wrong value when balance reaches cap](https://0xsimao.com/findings/m-0-unrealized-inflation-returns-reaches) - [Custom error for overflowing the total principal is not raised](https://0xsimao.com/findings/m-0-custom-overflowing-principal-raised) - [Proposals in the same voting period can have different ids but do the same](https://0xsimao.com/findings/m-0-proposals-voting-period-ids) - [Function cancelMint can be frontrunned to grief a validator](https://0xsimao.com/findings/m-0-mint-frontrunned-grief-validator) - [StandardGovernor's implementation of quorum is incompatible with Tally](https://0xsimao.com/findings/m-0-implementation-quorum-incompatible-tally) ## Informational findings - [Missing override keyword for interface inherited methods](https://0xsimao.com/findings/m-0-override-keyword-inherited-methods) - [Some contracts don't implement their entire interface](https://0xsimao.com/findings/m-0-don-implement-entire-interface) - [No need to set isActive to false if that mapping entry was deleted](https://0xsimao.com/findings/m-0-active-mapping-entry-deleted) - [Unnecessary Recomputation of Storage Pointer in MToken._startEarning](https://0xsimao.com/findings/m-0-recomputation-storage-pointer-earning) - [Unnecessary check in StandardGovernor.state](https://0xsimao.com/findings/m-0-unnecessary-standard-governor-state) - [Code should not panic underflow](https://0xsimao.com/findings/m-0-code-panic-underflow) - [StartedEarning event is emitted even if account is already earning](https://0xsimao.com/findings/m-0-started-earning-emitted-already) - [Wrong comment in Standard Governor's execute function](https://0xsimao.com/findings/m-0-comment-standard-governor-function) - [Unnecessary currentEpoch zero check in StandardGovernor and ThresholdGovernor](https://0xsimao.com/findings/m-0-current-epoch-zero-threshold) - [Overflow check in PowerToken._divideUp is unnecessary](https://0xsimao.com/findings/m-0-overflow-power-divide-unnecessary) - [Unnecessary conditional check in ThresholdGovernance.execute](https://0xsimao.com/findings/m-0-unnecessary-conditional-threshold-governance) - [Inconsistent naming of function in PureEpochs](https://0xsimao.com/findings/m-0-inconsistent-naming-pure-epochs) - [_checkAndIncrementNonce in ERC5805 raises a ReusedNonce error for non used nonces](https://0xsimao.com/findings/m-0-nonce-erc5805-raises-nonces) - [castVoteWithReason always fires a VoteCast event with an empty reason](https://0xsimao.com/findings/m-0-cast-vote-reason-fires) - [transferFrom in ERC20Extended will always emit an Approval event if the allowance changes](https://0xsimao.com/findings/m-0-transfer-erc20-approval-allowance) - [EIP712's _revertIfError should use all SignatureChecker.Error errors](https://0xsimao.com/findings/m-0-eip712-revert-signature-checker) - [The IERC3009 interface is not fully conforming to the standard](https://0xsimao.com/findings/m-0-ierc3009-interface-fully-conforming) ## The report [Download the report (PDF)](https://0xsimao.com/reports/2024-01-08-m-0.pdf)