Prototype pollution attack in node.extend

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`: ```javascript 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