[SECURITY] Missing Zero-Address Check in updateGovernanceProposer

[evmparser]

Summary

The updateGovernanceProposer function in Governance.sol prevents setting the proposer to the governance contract itself but fails to prevent setting it to the zero address.

Severity

MEDIUM - Could permanently disable standard proposal mechanism

Location

• File: l1-contracts/src/governance/Governance.sol
• Function: updateGovernanceProposer

Description

The function has incomplete validation:

function updateGovernanceProposer(address _governanceProposer) external override(IGovernance) onlySelf {
    require(_governanceProposer != address(this), Errors.Governance__GovernanceProposerCannotBeSelf());
    // Missing: require(_governanceProposer != address(0), "Cannot set to zero address");
    governanceProposer = _governanceProposer;
    emit GovernanceProposerUpdated(_governanceProposer);
}

Impact

If proposer is set to address(0):

• Standard propose() function becomes permanently disabled
• Only proposeWithLock() (emergency mechanism) remains functional
• Much higher barrier to entry for creating proposals
• Requires another governance proposal to fix (if emergency proposals can pass)

Attack Vector:

• Malicious proposal could intentionally set proposer to zero address
• Accidental misconfiguration during governance update

Recommendation

Add zero-address validation:

function updateGovernanceProposer(address _governanceProposer) external override(IGovernance) onlySelf {
    require(_governanceProposer != address(this), Errors.Governance__GovernanceProposerCannotBeSelf());
    require(_governanceProposer != address(0), "Proposer cannot be zero address");
    governanceProposer = _governanceProposer;
    emit GovernanceProposerUpdated(_governanceProposer);
}

Additional Context

The function already validates against address(this), showing awareness of invalid addresses. The zero-address check should be added for completeness.