fix: add __proto__ to objects and arrays

CHANGELOG.md

@@ -1,3 +1,12 @@
+### Unreleased [[code][c-unreleased], [diff][d-unreleased]]
+
+[c-unreleased]: https://github.com/json5/json5/tree/v1
+[d-unreleased]: https://github.com/json5/json5/compare/v1.0.1...v1
+
+- Fix: Properties with the name `__proto__` are added to objects and arrays.
+  ([#199])
+
+
 ### v1.0.1 [[code][c1.0.1], [diff][d1.0.1]]
 
 [c1.0.1]: https://github.com/json5/json5/tree/v1.0.1
@@ -272,3 +281,4 @@ parser for the regular JSON format.
 [#108]: https://github.com/json5/json5/pull/108
 [#134]: https://github.com/json5/json5/pull/134
 [#154]: https://github.com/json5/json5/issues/154
+[#199]: https://github.com/json5/json5/issues/199

src/parse.js

@@ -42,12 +42,34 @@ export default function parse (text, reviver) {
 function internalize (holder, name, reviver) {
     const value = holder[name]
     if (value != null && typeof value === 'object') {
-        for (const key in value) {
-            const replacement = internalize(value, key, reviver)
-            if (replacement === undefined) {
-                delete value[key]
-            } else {
-                value[key] = replacement
+        if (Array.isArray(value)) {
+            for (let i = 0; i < value.length; i++) {
+                const key = String(i)
+                const replacement = internalize(value, key, reviver)
+                if (replacement === undefined) {
+                    delete value[key]
+                } else {
+                    Object.defineProperty(value, key, {
+                        value: replacement,
+                        writable: true,
+                        enumerable: true,
+                        configurable: true,
+                    })
+                }
+            }
+        } else {
+            for (const key in value) {
+                const replacement = internalize(value, key, reviver)
+                if (replacement === undefined) {
+                    delete value[key]
+                } else {
+                    Object.defineProperty(value, key, {
+                        value: replacement,
+                        writable: true,
+                        enumerable: true,
+                        configurable: true,
+                    })
+                }
             }
         }
     }
@@ -973,7 +995,12 @@ function push () {
         if (Array.isArray(parent)) {
             parent.push(value)
         } else {
-            parent[key] = value
+            Object.defineProperty(parent, key, {
+                value,
+                writable: true,
+                enumerable: true,
+                configurable: true,
+            })
         }
     }
 

test/parse.js

@@ -33,6 +33,11 @@ describe('JSON5', () => {
                 assert.deepStrictEqual(JSON5.parse('{\\u0061\\u0062:1,\\u0024\\u005F:2,\\u005F\\u0024:3}'), {ab: 1, $_: 2, _$: 3})
             })
 
+            it('preserves __proto__ property names', () => {
+                // eslint-disable-next-line no-proto
+                assert.strictEqual(JSON5.parse('{"__proto__":1}').__proto__, 1)
+            })
+
             it('parses multiple properties', () => {
                 assert.deepStrictEqual(JSON5.parse('{abc:1,def:2}'), {abc: 1, def: 2})
             })