Information Disclosure via X-Content-Encoded-By Header

Description

The 'X-Content-Encoded-By' header may disclose the specific tool, module, or system used to encode or compress the response content. By revealing details about the encoding process, attackers might determine the underlying software or components in use, potentially correlating them with known vulnerabilities or misconfigurations. Moreover, an explicit encoding tool identifier can guide adversaries in crafting exploits that take advantage of compression-based or content transformation bugs. Disclosing this header expands the application's attack surface by providing additional insight into the server’s internal mechanisms and software dependencies.

Remediation

Remove or mask the 'X-Content-Encoded-By' header in production environments to avoid revealing sensitive encoding details. Configure your web server, application framework, or any associated compression/encoding modules to suppress or rename this header. If a reverse proxy or load balancer is present, ensure it does not reintroduce or preserve this header in the response. Keep all encoding or compression libraries up to date with the latest security patches. Employ a Web Application Firewall (WAF) or intrusion detection system to detect and block suspicious traffic attempting to exploit known encoding vulnerabilities. Periodically review response headers to ensure no unnecessary information is leaked about server-side content handling processes.

References

Severity

Owasp

Code: A05:2021

Category: Security Misconfiguration

Classification