Introduction

In this post, we will give a breakdown of a lesser-known vulnerability called Prototype Pollution, which is centered around JavaScript prototypes. JavaScript is built around prototypes, which are like blueprints for objects. When an object is created, it can inherit properties and methods from its prototype. For example:

const obj = {};

console.log(obj.toString()); // Inherited from Object.prototype

However, if someone finds a way to mess with the prototype, it can affect every object that uses that blueprint. Attacks can inject fake properties into the prototype, making the app behave in unexpected or dangerous ways.

Frameworks & Environments Affected by Prototype Pollution

Prototype pollution is particularly relevant in JavaScript-based environments and ecosystems. Below are some commonly affect frameworks, libraries, and scenarios:

Popular Utility Libraries

Historically, libraries like jquery, deepmerge, and lodash have been susceptible to prototype pollution. If user inputs are not adequately sanitized, applications that depend on these libraries for deep object merging or manipulation may inadvertently leave themselves vulnerable to attacks.

Frontend Frameworks

Vue.js, Angular, React, and other frameworks are not intrinsically weak. Vulnerabilities may be introduced, nevertheless, if user-provided data is handled incorrectly during state management or object manipulation. Prototype pollution could result, for instance, from combining external inputs into a React state object without first sanitizing them.

Web Frameworks & Middleware

Incoming data (query parameters, JSON payloads) is frequently parsed into objects by Express.js and related frameworks. Attackers may be able to alter global object prototypes if appropriate filtering is not in place.

APIs Processing JSON Payloads

When JSON data is handled by APIs without sufficient validation, prototype pollution may spread across the program. In applications with multiple users or tenants, malicious payloads injected via __proto__ properties might cause serious problems.

Conclusion

Though uncommon, prototype pollution can have devasting effects on web applications when exploited impacting everything from functionality to security. Its reach extends across various frameworks and libraries, making awareness and vigilance essential for developers. In the next post, we will delve into some real-world examples and explore mitigation techniques.

Hexadius Consulting provides Vulnerability Assessments and Penetration Testing (VAPT) services to identify and mitigate risks like prototype pollution through comprehensive security audits, tailored remediation strategies, and proactive risk management. Our team provides end-to-end support, from uncovering vulnerabilities in your codebase to implementing robust defenses and equipping your team with the knowledge to prevent future issues. If you’re concerned about the security of your systems, contact us today to safeguard your applications, protect your data, and ensure business continuity.

Reference: https://portswigger.net/web-security/prototype-pollution