One of the critical yet often overlooked vulnerabilities in web applications is the disclosure of excessive information in HTTP response headers. When response headers reveal details about the server and application, attackers can exploit this information to identify potential security flaws, including zero-day vulnerabilities.
This vulnerability arises when servers and application frameworks often include default headers that reveal their version, name or other details (e.g., X-Powered-By: PHP/8.1.2 or Server: Apache/2.4.52). Developers or system administrators fail to limit or sanitize the information included in the response headers. During development, verbose headers are useful for troubleshooting but are sometimes left exposed in production environments.