fix: Unweighted Oracle Standard Deviation Inflates Reward Band

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 ### Fixed
 
+- Compute the oracle ballot `StandardDeviation` as a stake-weighted variance (weight each squared deviation by the vote's power and divide by total voting power) instead of an unweighted average divided by the vote count, aligning the reward-band width with the stake-weighted median and preventing a group of low-stake validators from inflating the deviation to widen the accepted vote window
 - Remove the forced minimum 1-unit-per-block reward release in `CalculateReward` and skip (instead of deactivating) sub-unit blocks in the rewards `BeginBlocker`, so the proportional share accumulates and the pool follows the configured schedule independent of block time (previously a 10-year, 1M-unit schedule drained in ~12 days at the 1s target block time and ~28 days at the current ~2.4s rate, regardless of the configured duration)
 - Reject `MsgEthereumTx` from being dispatched through the authz keeper (including when nested inside `authz.MsgExec`), closing an EVM ante bypass on message-router execution paths that skip the ante handler
 - Fix feegrant denomination bypass in the cosmos fee ante handler by converting the fee before consuming the grant, so `UseGrantedFees` is checked against the same coins later deducted (prevents a grantee from forcing the granter to pay in a non-granted fee-abstraction denom)

x/oracle/types/ballot.go

@@ -173,20 +173,26 @@ func (ex ExchangeRateBallot) StandardDeviation(median sdkMath.LegacyDec) (standa
 		}
 	}()
 
+	// Get the total voting power to weight the variance
+	totalPower := ex.Power()
+	if totalPower == 0 {
+		return sdkMath.LegacyZeroDec()
+	}
+
 	sum := sdkMath.LegacyZeroDec()
 	for _, votes := range ex {
-		deviation := votes.ExchangeRate.Sub(median) // calculate the ex - median
-		sum = sum.Add(deviation.Mul(deviation))     // Calculate sum += (ex - median)^2
+		deviation := votes.ExchangeRate.Sub(median)                   // calculate the ex - median
+		sum = sum.Add(deviation.Mul(deviation).MulInt64(votes.Power)) // Calculate sum += power * (ex - median)^2
 	}
 
-	// Divide the result by the number of ex
-	variance := sum.QuoInt64(int64(len(ex)))
+	// Divide the result by the total voting power
+	variance := sum.QuoInt64(totalPower)
 
 	// Finally get the square root of variance
 	standardDeviation, err := variance.ApproxSqrt()
 	if err != nil {
 		return sdkMath.LegacyZeroDec()
 	}
 
-	return
+	return standardDeviation
 }

x/oracle/types/ballot_test.go

@@ -180,7 +180,7 @@ func TestStandardDeviation(t *testing.T) {
 	median := ballot.WeightedMedianWithAssertion()
 	deviation := ballot.StandardDeviation(median)
 
-	expected := sdkMath.LegacyNewDecWithPrec(1224745, 6)
+	expected := sdkMath.LegacyOneDec()
 	// 2e-7 tolerance
 	delta := sdkMath.LegacyNewDecWithPrec(2, 7)