Make _.memoize skip the __proto__ key.

lodash.js

@@ -5340,9 +5340,11 @@
         throw new TypeError(funcErrorText);
       }
       var memoized = function() {
-        var cache = memoized.cache,
-            key = resolver ? resolver.apply(this, arguments) : '_' + arguments[0];
-
+        var key = resolver ? resolver.apply(this, arguments) : arguments[0];
+        if (key == '__proto__') {
+          return func.apply(this, arguments);
+        }
+        var cache = memoized.cache;
         return hasOwnProperty.call(cache, key)
           ? cache[key]
           : (cache[key] = func.apply(this, arguments));

test/test.js

@@ -3443,15 +3443,6 @@
       deepEqual(_.uniq(largeArray), expected);
       deepEqual(_.without.apply(_, [largeArray].concat(largeArray)), []);
     });
-
-    test('lodash.memoize should support values that resolve to the `__proto__` key', 1, function() {
-      var count = 0,
-          memoized = _.memoize(function() { return ++count; });
-
-      memoized('__proto__');
-      memoized('__proto__');
-      strictEqual(count, 1);
-    });
   }());
 
   /*--------------------------------------------------------------------------*/
@@ -6098,16 +6089,35 @@
     });
 
     test('should expose a `cache` object on the `memoized` function', 4, function() {
-      _.each(['_a', 'a'], function(key, index) {
-        var memoized = _.memoize(_.identity, index && _.identity);
+      _.times(2, function(index) {
+        var resolver = index && _.identity,
+            memoized = _.memoize(_.identity, resolver);
 
         memoized('a');
-        strictEqual(memoized.cache[key], 'a');
+        strictEqual(memoized.cache.a, 'a');
 
-        memoized.cache[key] = 'b';
+        memoized.cache.a = 'b';
         strictEqual(memoized('a'), 'b');
       });
     });
+
+    test('should skip the `__proto__` key', 4, function() {
+      _.times(2, function(index) {
+        var count = 0,
+            resolver = index && _.identity;
+
+        var memoized = _.memoize(function() {
+          count++;
+          return [];
+        }, resolver);
+
+        memoized('__proto__');
+        memoized('__proto__');
+
+        strictEqual(count, 2);
+        ok(!(memoized.cache instanceof Array));
+      });
+    });
   }());
 
   /*--------------------------------------------------------------------------*/