Which plugin parses HTTP traffic and applies a set of rules before sending it to the application server?

The correct answer is the Web Application Firewall (WAF). A WAF acts as a security layer that monitors and filters HTTP traffic between a web application and the internet. It analyzes incoming traffic and applies a series of predefined security rules to determine if the traffic is safe or possibly malicious. By doing so, it helps protect web applications from various threats such as SQL injection, cross-site scripting (XSS), and other OWASP Top Ten vulnerabilities.

This role is critical in maintaining the integrity and availability of web applications, particularly in cloud environments where applications are often exposed to a wider array of potential risks. By parsing HTTP traffic, a WAF can detect and block harmful requests before they reach the application server, thus serving as an essential measure in an organization's security posture.