Add __proto__ guards to more methods.

lodash.js

@@ -2383,7 +2383,7 @@
     function assignMergeValue(object, key, value) {
       if ((value !== undefined && !eq(object[key], value)) ||
           (typeof key == 'number' && value === undefined && !(key in object))) {
-        object[key] = value;
+        baseAssignValue(object, key, value);
       }
     }
 
@@ -2401,16 +2401,7 @@
       var objValue = object[key];
       if (!(hasOwnProperty.call(object, key) && eq(objValue, value)) ||
           (value === undefined && !(key in object))) {
-        if (key == '__proto__' && defineProperty) {
-          defineProperty(object, key, {
-            'configurable': true,
-            'enumerable': true,
-            'value': value,
-            'writable': true
-          });
-        } else {
-          object[key] = value;
-        }
+        baseAssignValue(object, key, value);
       }
     }
 
@@ -2463,6 +2454,28 @@
       return object && copyObject(source, keys(source), object);
     }
 
+    /**
+     * The base implementation of `assignValue` and `assignMergeValue` without
+     * value checks.
+     *
+     * @private
+     * @param {Object} object The object to modify.
+     * @param {string} key The key of the property to assign.
+     * @param {*} value The value to assign.
+     */
+    function baseAssignValue(object, key, value) {
+      if (key == '__proto__' && defineProperty) {
+        defineProperty(object, key, {
+          'configurable': true,
+          'enumerable': true,
+          'value': value,
+          'writable': true
+        });
+      } else {
+        object[key] = value;
+      }
+    }
+
     /**
      * The base implementation of `_.at` without support for individual paths.
      *
@@ -3650,7 +3663,7 @@
             value = object[key];
 
         if (predicate(value, key)) {
-          result[key] = value;
+          baseAssignValue(result, key, value);
         }
       }
       return result;
@@ -4617,6 +4630,7 @@
      * @returns {Object} Returns `object`.
      */
     function copyObject(source, props, object, customizer) {
+      var isNew = !object;
       object || (object = {});
 
       var index = -1,
@@ -4629,7 +4643,14 @@
           ? customizer(object[key], source[key], key, object, source)
           : undefined;
 
-        assignValue(object, key, newValue === undefined ? source[key] : newValue);
+        if (newValue === undefined) {
+          newValue = source[key];
+        }
+        if (isNew) {
+          baseAssignValue(object, key, newValue);
+        } else {
+          assignValue(object, key, newValue);
+        }
       }
       return object;
     }
@@ -8749,7 +8770,11 @@
      * // => { '3': 2, '5': 1 }
      */
     var countBy = createAggregator(function(result, value, key) {
-      hasOwnProperty.call(result, key) ? ++result[key] : assignValue(result, key, 1);
+      if (hasOwnProperty.call(result, key)) {
+        ++result[key];
+      } else {
+        baseAssignValue(result, key, 1);
+      }
     });
 
     /**
@@ -9072,7 +9097,7 @@
       if (hasOwnProperty.call(result, key)) {
         result[key].push(value);
       } else {
-        assignValue(result, key, [value]);
+        baseAssignValue(result, key, [value]);
       }
     });
 
@@ -9185,7 +9210,7 @@
      * // => { 'left': { 'dir': 'left', 'code': 97 }, 'right': { 'dir': 'right', 'code': 100 } }
      */
     var keyBy = createAggregator(function(result, value, key) {
-      assignValue(result, key, value);
+      baseAssignValue(result, key, value);
     });
 
     /**
@@ -13008,7 +13033,7 @@
       iteratee = getIteratee(iteratee, 3);
 
       baseForOwn(object, function(value, key, object) {
-        result[iteratee(value, key, object)] = value;
+        baseAssignValue(result, iteratee(value, key, object), value);
       });
       return result;
     }
@@ -13046,7 +13071,7 @@
       iteratee = getIteratee(iteratee, 3);
 
       baseForOwn(object, function(value, key, object) {
-        result[key] = iteratee(value, key, object);
+        baseAssignValue(result, key, iteratee(value, key, object));
       });
       return result;
     }
@@ -14900,7 +14925,7 @@
     var bindAll = baseRest(function(object, methodNames) {
       arrayEach(baseFlatten(methodNames, 1), function(key) {
         key = toKey(key);
-        object[key] = bind(object[key], object);
+        baseAssignValue(object, key, bind(object[key], object));
       });
       return object;
     });