fix: patch prototype pollution vulnerability in deepMix and mix by Copilot · Pull Request #131 · antvis/util

Copilot · 2026-03-03T14:12:05Z

Fix _deepMix in src/lodash/deep-mix.ts to skip dangerous keys (__proto__, constructor, prototype)
Add unit tests for deepMix with prototype pollution regression cases
Fix _mix in src/lodash/mix.ts to also skip __proto__ and prototype keys
Add unit tests for mix with prototype pollution regression cases
Bump version to 3.3.12

Original prompt

The Issue #130 in the @antv/util repository highlights a critical Prototype Pollution vulnerability in the deepMix function for versions <= 3.3.11. The deepMix function does not validate keys when merging objects, leading to potential modifications of Object.prototype properties. Attackers can exploit this to execute Denial of Service (DoS), authentication bypass, or remote code execution (RCE).

Proposed Fix:

Update the deepMix function to include validation to prevent prototype pollution.

Specifically, check keys such as __proto__, constructor, and prototype in the for-in loop before assignment.

Add a regression test to ensure the deepMix function is resilient against object prototype pollution attacks.

Tasks:

Modify the deepMix function in the file src/esm/lodash/deep-mix.js to prevent prototype modification.

Write unit tests to validate the deepMix implementation with edge cases and malicious payloads from Issue Reference.

Refactor and document the changes with in-place comments explaining the implementation.

Update other references within the codebase to include the fixed deepMix function.

Provide fixes and bash files supporting NPM validation when hit locally.

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Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

hustcc · 2026-04-05T23:51:15Z

@copilot mix 方法是不是也有类似的问题

Agent-Logs-Url: https://github.com/antvis/util/sessions/7731b37f-784f-4d46-bfc5-ea4bf127da73 Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

Copilot · 2026-04-05T23:53:24Z

@copilot mix 方法是不是也有类似的问题

是的，mix 也有同样的问题——它只屏蔽了 constructor，但缺少对 __proto__ 和 prototype 的防护。已在 cfde1e3 修复，同时新增了回归测试。

hustcc · 2026-04-06T00:01:53Z

@copilot 升级版本号，我准备发版本。

Agent-Logs-Url: https://github.com/antvis/util/sessions/4c19cc22-f38e-4578-b3f6-9bc3d30b8ccf Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

Copilot · 2026-04-06T00:02:41Z

@copilot 升级版本号，我准备发版本。

已在 965c783 将版本号从 3.3.11 升级到 3.3.12。

Copilot

Pull request overview

This PR patches a prototype pollution vulnerability in the object-merge utilities (deepMix and mix) by skipping dangerous keys during merges, and adds regression tests to prevent reintroduction.

Changes:

Add __proto__ / constructor / prototype key skipping guards in src/lodash/deep-mix.ts and src/lodash/mix.ts.
Add new Jest unit tests covering standard merge behavior and prototype pollution vectors for both functions.
Update .gitignore to ignore package-lock.json.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`src/lodash/mix.ts`	Adds an early-continue guard for prototype-pollution keys during shallow merge.
`src/lodash/deep-mix.ts`	Adds a similar guard inside the `hasOwn` check during deep merge recursion.
`__tests__/unit/lodash/mix.spec.ts`	Introduces regression tests for `mix` merge behavior and pollution vectors.
`__tests__/unit/lodash/deep-mix.spec.ts`	Introduces regression tests for `deepMix` merge behavior and pollution vectors.
`.gitignore`	Ignores `package-lock.json`.

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Copilot · 2026-04-06T00:04:01Z

+    ) {
+      continue;
+    }
+    if (obj.hasOwnProperty(key) && obj[key] !== undefined) {


_mix uses obj.hasOwnProperty(key), which can throw for Object.create(null) inputs and can be overridden on attacker-controlled objects. Use a safe check like Object.prototype.hasOwnProperty.call(obj, key) (or reuse the hasOwn helper pattern from deep-mix.ts) to avoid DoS and ensure the guard is reliable.

Suggested change

if (obj.hasOwnProperty(key) && obj[key] !== undefined) {

if (Object.prototype.hasOwnProperty.call(obj, key) && obj[key] !== undefined) {

Copilot · 2026-04-06T00:04:02Z

@@ -0,0 +1,25 @@
+import mix from '../../../src/lodash/mix';


These tests import the implementation file directly. Most existing lodash unit tests import via ../../../src/lodash (public entrypoint), which better matches consumer usage and also ensures the index exports stay correct. Consider switching to import { mix } from '../../../src/lodash'.

Suggested change

import mix from '../../../src/lodash/mix';

import { mix } from '../../../src/lodash';

Copilot · 2026-04-06T00:04:02Z

+  it('does not pollute Object.prototype via __proto__', () => {
+    const payload = JSON.parse('{"__proto__": {"polluted": true}}');
+    mix({}, payload);
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });
+
+  it('does not pollute via constructor key', () => {
+    const payload = JSON.parse('{"constructor": {"prototype": {"polluted": true}}}');
+    mix({}, payload);
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });
+
+  it('does not pollute via prototype key', () => {
+    mix({} as any, { prototype: { polluted: true } } as any);
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });


Prototype-pollution regression tests mutate global state if the protection ever regresses, which can cascade failures into unrelated tests. Add a beforeEach/afterEach cleanup (e.g., delete (Object.prototype as any).polluted) to keep the suite isolated and deterministic.

Copilot · 2026-04-06T00:04:02Z

@@ -0,0 +1,30 @@
+import deepMix from '../../../src/lodash/deep-mix';


These tests import the implementation file directly. Most existing lodash unit tests import via ../../../src/lodash (public entrypoint), which better matches consumer usage and also ensures the index exports stay correct. Consider switching to import { deepMix } from '../../../src/lodash'.

Suggested change

import deepMix from '../../../src/lodash/deep-mix';

import { deepMix } from '../../../src/lodash';

Copilot · 2026-04-06T00:04:02Z

+  it('does not pollute Object.prototype via __proto__', () => {
+    const payload = JSON.parse('{"__proto__": {"polluted": true}}');
+    deepMix({}, payload);
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });
+
+  it('does not pollute via constructor.prototype', () => {
+    const payload = JSON.parse('{"constructor": {"prototype": {"polluted": true}}}');
+    deepMix({}, payload);
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });
+
+  it('does not pollute via prototype key', () => {
+    deepMix({}, { prototype: { polluted: true } });
+    expect((Object.prototype as any).polluted).toBeUndefined();
+  });


Prototype-pollution regression tests can leave Object.prototype modified if the guard breaks, affecting later tests and making failures harder to interpret. Add cleanup in beforeEach/afterEach (e.g., delete (Object.prototype as any).polluted) to keep tests isolated.

nrps9909

AI assistance disclosure: Codex was used to trace the downstream Ant Design Charts report to this utility, reproduce the published exploit, inspect this exact diff, run the repository validation, and construct the additional adversarial probes below. I verified every reported result before submitting this review.

Reviewed exact head 965c783 against base 426c79b.

The dangerous-key guard in deepMix does block the currently published payload: after building this head, merging JSON.parse of the proto payload leaves Object.prototype unchanged. However, the security hardening added to mix still trusts the attacker-controlled source method at src/lodash/mix.ts:12:

obj.hasOwnProperty(key)

Two independent exact-head regressions fail before any safe property can be copied:

mix({}, Object.assign(Object.create(null), { safe: true }))
TypeError: obj.hasOwnProperty is not a function
mix({}, JSON.parse of { hasOwnProperty: null, safe: true })
TypeError: obj.hasOwnProperty is not a function

Because mix is now explicitly included in this vulnerability fix, source ownership needs to be checked independently of the source object, for example with Object.prototype.hasOwnProperty.call or the same null-safe hasOwn helper already present in deep-mix.ts. Please add both null-prototype and shadowed-hasOwnProperty regressions so an untrusted merge source cannot turn the security path into a controllable denial of service.

There is also one changed-file gate failure: Prettier reports src/lodash/mix.ts as unformatted and collapses the multiline dangerous-key condition.

Validation summary:

existing focused deepMix and mix tests: 8 passed
independent security matrix: original pollution case passed; the two ownership cases failed
complete repository: 35 suites and 107 tests passed
CommonJS, ESM, and UMD builds plus both size limits passed
ESLint reported zero errors and three pre-existing warnings
full lint remained red for three Prettier files, including changed src/lodash/mix.ts; the other two are unchanged base files

This is a narrowly scoped request: retain the current dangerous-key guard, make the ownership check source-independent, add the two regressions, and format the changed source. The downstream @ant-design/plots 2.6.8 / @antv/g2 5.4.8 reproduction remains exploitable while @antv/util 3.3.11 is the published version.

Initial plan

09edb08

Copilot AI assigned Copilot and hustcc Mar 3, 2026

Copilot started work on behalf of hustcc March 3, 2026 14:12 View session

Copilot AI and others added 2 commits March 3, 2026 14:16

fix: prevent prototype pollution in deepMix

584a7e6

Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

chore: ignore package-lock.json

879be4a

Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix prototype pollution vulnerability in deepMix function~~ fix: patch prototype pollution vulnerability in deepMix Mar 3, 2026

Copilot finished work on behalf of hustcc March 3, 2026 14:17

hustcc marked this pull request as ready for review March 3, 2026 14:29

Copilot started work on behalf of hustcc April 5, 2026 23:51 View session

fix: prevent prototype pollution in mix function

cfde1e3

Agent-Logs-Url: https://github.com/antvis/util/sessions/7731b37f-784f-4d46-bfc5-ea4bf127da73 Co-authored-by: hustcc <7856674+hustcc@users.noreply.github.com>

Copilot AI changed the title ~~fix: patch prototype pollution vulnerability in deepMix~~ fix: patch prototype pollution vulnerability in deepMix and mix Apr 5, 2026

Copilot AI requested a review from hustcc April 5, 2026 23:54

Copilot finished work on behalf of hustcc April 5, 2026 23:54

hustcc approved these changes Apr 6, 2026

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hustcc requested a review from Copilot April 6, 2026 00:01

Copilot started reviewing on behalf of hustcc April 6, 2026 00:01 View session

Copilot started work on behalf of hustcc April 6, 2026 00:02 View session

chore: bump version to 3.3.12

965c783

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Copilot AI requested a review from hustcc April 6, 2026 00:03

Copilot finished work on behalf of hustcc April 6, 2026 00:03

Copilot AI reviewed Apr 6, 2026

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hustcc approved these changes Apr 6, 2026

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nrps9909 suggested changes Sep 4, 2026

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nrps9909 mentioned this pull request Sep 4, 2026

[Bug]: Prototype Pollution via Exported G2.renderToMountedElement Options ant-design/ant-design-charts#3163

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hustcc approved these changes Oct 9, 2026

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hustcc merged commit dffe157 into master Oct 9, 2026
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hustcc deleted the copilot/fix-prototype-pollution-vulnerability branch October 9, 2026 01:40

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fix: patch prototype pollution vulnerability in deepMix and mix - #131

fix: patch prototype pollution vulnerability in deepMix and mix#131
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	if (obj.hasOwnProperty(key) && obj[key] !== undefined) {
	if (Object.prototype.hasOwnProperty.call(obj, key) && obj[key] !== undefined) {

	import mix from '../../../src/lodash/mix';
	import { mix } from '../../../src/lodash';

		@@ -0,0 +1,30 @@
		import deepMix from '../../../src/lodash/deep-mix';

	import deepMix from '../../../src/lodash/deep-mix';
	import { deepMix } from '../../../src/lodash';

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