Fix: prevent prototype pollution by validating dynamic keys across controllers

packages/assets-controllers/src/AccountTrackerController.ts

@@ -704,6 +704,14 @@ export class AccountTrackerController extends StaticIntervalPollingController<Ac
   ) {
     this.update((state) => {
       balances.forEach(({ address, chainId, balance }) => {
+        // Prevent prototype pollution with dangerous keys
+        if (
+          chainId === '__proto__' ||
+          chainId === 'constructor' ||
+          chainId === 'prototype'
+        ) {
+          return;
+        }
         const checksumAddress = toChecksumHexAddress(address);
 
         // Ensure the chainId exists in the state
@@ -740,6 +748,14 @@ export class AccountTrackerController extends StaticIntervalPollingController<Ac
   ) {
     this.update((state) => {
       stakedBalances.forEach(({ address, chainId, stakedBalance }) => {
+        // Prevent prototype pollution with dangerous keys
+        if (
+          chainId === '__proto__' ||
+          chainId === 'constructor' ||
+          chainId === 'prototype'
+        ) {
+          return;
+        }
         const checksumAddress = toChecksumHexAddress(address);
 
         // Ensure the chainId exists in the state

packages/assets-controllers/src/TokenBalancesController.ts

@@ -594,6 +594,14 @@ export class TokenBalancesController extends StaticIntervalPollingController<{
       // First, initialize all tokens from allTokens state with balance 0
       // for the accounts and chains we're processing
       for (const chainId of targetChains) {
+        // Prevent prototype pollution by skipping dangerous property names
+        if (
+          chainId === '__proto__' ||
+          chainId === 'constructor' ||
+          chainId === 'prototype'
+        ) {
+          continue;
+        }
         for (const account of accountsToProcess) {
           // Initialize tokens from allTokens
           const chainTokens = this.#allTokens[chainId];
@@ -625,6 +633,14 @@ export class TokenBalancesController extends StaticIntervalPollingController<{
 
       // Then update with actual fetched balances where available
       aggregated.forEach(({ success, value, account, token, chainId }) => {
+        // Prevent prototype pollution by skipping dangerous property names
+        if (
+          chainId === '__proto__' ||
+          chainId === 'constructor' ||
+          chainId === 'prototype'
+        ) {
+          return;
+        }
         if (success && value !== undefined) {
           ((d.tokenBalances[account] ??= {})[chainId] ??= {})[checksum(token)] =
             toHex(value);

packages/earn-controller/src/selectors.ts

@@ -23,11 +23,13 @@ export const selectLendingMarketsByProtocolAndId = createSelector(
   (markets) => {
     return markets.reduce(
       (acc, market) => {
-        acc[market.protocol] = acc[market.protocol] || {};
-        acc[market.protocol][market.id] = market;
+        if (!acc.has(market.protocol)) {
+          acc.set(market.protocol, new Map());
+        }
+        acc.get(market.protocol)!.set(market.id, market);
         return acc;
       },
-      {} as Record<string, Record<string, LendingMarket>>,
+      new Map<string, Map<string, LendingMarket>>(),
     );
   },
 );
@@ -38,7 +40,9 @@ export const selectLendingMarketForProtocolAndId = (
 ) =>
   createSelector(
     selectLendingMarketsByProtocolAndId,
-    (marketsByProtocolAndId) => marketsByProtocolAndId?.[protocol]?.[id],
+    (marketsByProtocolAndId) => {
+      return marketsByProtocolAndId?.get(protocol)?.get(id);
+    },
   );
 
 export const selectLendingMarketsByChainId = createSelector(
@@ -63,7 +67,7 @@ export const selectLendingPositionsWithMarket = createSelector(
       return {
         ...position,
         market:
-          marketsByProtocolAndId?.[position.protocol]?.[position.marketId],
+          marketsByProtocolAndId?.get(position.protocol)?.get(position.marketId),
       };
     });
   },

packages/ens-controller/src/EnsController.ts

@@ -196,11 +196,14 @@ export class EnsController extends BaseController<
    */
   delete(chainId: Hex, ensName: string): boolean {
     const normalizedEnsName = normalizeEnsName(ensName);
+    // Defense-in-depth: block prototype-polluting property names.
+    const unsafeKeys = ['__proto__', 'prototype', 'constructor'];
     if (
       !isSafeDynamicKey(chainId) ||
       !normalizedEnsName ||
       !this.state.ensEntries[chainId] ||
-      !this.state.ensEntries[chainId][normalizedEnsName]
+      !this.state.ensEntries[chainId][normalizedEnsName] ||
+      unsafeKeys.includes(chainId)
     ) {
       return false;
     }

packages/name-controller/src/NameController.ts

@@ -467,14 +467,14 @@ export class NameController extends BaseController<
     }
 
     this.update((state) => {
-      const typeEntries = state.names[type] || {};
+      const typeEntries = state.names[type] || Object.create(null);
       state.names[type] = typeEntries;
 
-      const variationEntries = typeEntries[normalizedValue] || {};
+      const variationEntries = typeEntries[normalizedValue] || Object.create(null);
       typeEntries[normalizedValue] = variationEntries;
 
       const entry = variationEntries[normalizedVariation] ?? {
-        proposedNames: {},
+        proposedNames: Object.create(null),
         name: null,
         sourceId: null,
         origin: null,

packages/network-enablement-controller/src/NetworkEnablementController.ts

@@ -252,6 +252,17 @@ export class NetworkEnablementController extends BaseController<
       );
     }
 
+    // Prevent prototype pollution via dangerous property names
+    if (
+      namespace === '__proto__' ||
+      namespace === 'constructor' ||
+      namespace === 'prototype'
+    ) {
+      throw new Error(
+        `Invalid namespace: "${namespace}" is not allowed.`,
+      );
+    }
+
     this.update((s) => {
       // Ensure the namespace bucket exists
       this.#ensureNamespaceBucket(s, namespace);

packages/sample-controllers/src/sample-petnames-controller.ts

@@ -211,6 +211,14 @@ export class SamplePetnamesController extends BaseController<
     if (!isSafeDynamicKey(chainId)) {
       throw new Error('Invalid chain ID');
     }
+    // Explicitly forbid keys that may cause prototype pollution.
+    if (
+      chainId === '__proto__' ||
+      chainId === 'constructor' ||
+      chainId === 'prototype'
+    ) {
+      throw new Error('Unsafe chain ID');
+    }
 
     const normalizedAddress = address.toLowerCase() as Hex;