Security Testing REST APIs vs. WebSockets: What's The Difference?

Engineering teams often excel in REST API security testing due to well-defined structures and tools like OpenAPI specifications that facilitate automated scanning and vulnerability identification. However, when it comes to WebSockets, the absence of standardized specifications, along with their stateful, bidirectional nature, poses unique challenges. Unlike REST APIs, WebSockets maintain persistent connections and allow for freeform messaging, which complicates automated testing and requires a deeper understanding of application-specific protocols. WebSocket security testing demands manual efforts such as validating Origin headers, ensuring authentication and authorization on a per-message basis, and implementing robust input validation and connection limits to prevent vulnerabilities like Cross-Site WebSocket Hijacking (CSWSH). While the underlying vulnerability categories remain similar across both protocols, the methods for testing them differ significantly, necessitating a tailored approach to WebSocket security that complements existing REST API testing practices.