X-Content-Type-Options Header is Missing

Description

The absence of the X-Content-Type-Options response HTTP header may expose a website to MIME sniffing attacks. MIME sniffing, performed by browsers when the MIME type is not explicitly declared, can lead to the interpretation of non-executable content as executable, potentially exposing users to security risks.

Recommendation

To mitigate this risk, configure your server to send the X-Content-Type-Options header with the value set to nosniff. This instructs browsers not to perform MIME sniffing and to strictly respect the declared content type.

References

• Mozilla: Web Security
• Mozilla: X-Content-Type-Options
• Mozilla: MIME sniffing
• Mozilla: MIME types (IANA media types)
• OWASP: X-Content-Type-Options Header
• CWE-16
• OWASP 2021-A5