Video: Preventing JavaScript Prototype Pollution

Prototype pollution in JavaScript occurs when an arbitrary payload handled by the code can overwrite properties or methods on the prototype chain of one or multiple objects. This usually happens through functions like merging, where properties on the prototype can be unintentionally modified, leading to unexpected behavior or security vulnerabilities.

Prototype pollution can lead to security vulnerabilities such as unauthorized access, remote code execution, and other unintended behaviors within an application. It manipulates the prototype of an object, which all instances of objects inherit methods and properties from, potentially allowing attackers to exploit this for malicious purposes.

To prevent prototype pollution, developers can sanitize and validate incoming data to ensure it does not contain malicious inputs, use Object.create(null) to create objects with no prototype, avoid using vulnerable versions of functions like merge or extend, and employ libraries or tools that filter out prototype properties like __proto__.

Yes, using maps instead of plain JavaScript objects can help prevent prototype pollution because maps do not have a prototype that can be polluted. Maps store keys and values in a form that doesn't interfere with the object's prototype chain.

The __proto__ property in JavaScript is used to assign the prototype of an object. In the context of prototype pollution, malicious payloads can manipulate __proto__ to overwrite properties on an object's prototype chain, leading to potential security risks.

Prototype pollution can significantly impact third-party libraries by altering their behavior if these libraries do not properly guard against modifications to their prototype. This can lead to widespread issues across applications that utilize the affected libraries, compromising application integrity and security.

Real-world consequences of prototype pollution include unauthorized data access, application crashes, and remote code execution. Historical incidents have shown that prototype pollution can lead to significant security breaches, affecting large-scale systems and leading to data loss or corruption.