Increasing delegate eligibility score will make some delegatees instantly bumpable (skipping grace period)

[CergyK]

Description

The BinaryEligibilityOracleEarningPowerCalculator determines the earning power for a delegatee to be either 0 or 100% depending on the score of the delegatee is greater or below a threshold. When a delegatee first crosses below the threshold, a grace period is applied in order for the delegatee to not be instantly punished by a bump which would incentivize delegators to delegate to another.

BinaryEligibilityOracleEarningPowerCalculator.sol#L234-L242:

function _updateDelegateeScore(address _delegatee, uint256 _newScore) internal {
    uint256 _oldScore = delegateeScores[_delegatee];
    bool _previouslyEligible = _oldScore >= delegateeEligibilityThresholdScore;
    bool _newlyEligible = _newScore >= delegateeEligibilityThresholdScore;
    emit DelegateeScoreUpdated(_delegatee, _oldScore, _newScore);
    // Record the time if the new score crosses the eligibility threshold.
>>  if (_previouslyEligible && !_newlyEligible) timeOfIneligibility[_delegatee] = block.timestamp;
    delegateeScores[_delegatee] = _newScore;
}

BinaryEligibilityOracleEarningPowerCalculator.sol#L153-L157:

    if (!_isDelegateeEligible(_delegatee)) {
      bool _isUpdateDelayElapsed =
>>      (timeOfIneligibility[_delegatee] + updateEligibilityDelay) <= block.timestamp;
      return (0, _isUpdateDelayElapsed);
    }

However we can note that in the case the delegate eligibility score is updated, the criteria to see if the delegatee has just become ineligible returns false. This means that the calculator will consider that the delegatee was previously ineligible and the grace period will not apply

Recommendation

Please consider adding a timestamp lastEligibilityScoreUpdated which should also be compared against when determining grace period.

[alexkeating]

Wont fix