How it was found

I would like to report a prototype pollution vulnerability in node.extend. It allows an attacker to inject properties on Object.prototype.

Module

module name: node.extend version: 2.0.0 npm page: https://www.npmjs.com/package/node.extend

Module Description

A port of jQuery.extend that actually works on node.js

Module Stats

267,701 downloads in the last week

Vulnerability

Vulnerability Description

This is a variant of this vulnerability: https://hackerone.com/reports/310443

node.extend can be tricked into adding or modifying properties of the Object prototype. These properties will be present on all objects.

Steps To Reproduce:

Craft an object of form {__proto__: {...}} and send it to node.extend:

let extend = require('node.extend');
extend(true, {}, JSON.parse('{"__proto__": {"isAdmin": true}}'));
console.log({}.isAdmin); // true

Wrap up

• I contacted the maintainer to let them know: [N]
• I opened an issue in the related repository: [N]

Impact

Denial of service, possibly more depending on the application. See https://hackerone.com/reports/310443