R043. Define a explicit content type


All system files generated dynamically must have a Content-Type explicitly defined.


  1. CWE-116: Improper Encoding or Escaping of Output. The product does not validate or incorrectly validates input that can affect the control flow or data flow of a program.

  2. OWASP Top 10 A1:2017-Injection. Injection flaws, such as SQL, NoSQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization.

  3. OWASP Top 10 A6:2017-Security Misconfiguration. Security misconfiguration is the most commonly seen issue. This is commonly a result of insecure default configurations, incomplete or ad hoc configurations, open cloud storage, misconfigured HTTP headers, and verbose error messages containing sensitive information. Not only must all operating systems, frameworks, libraries, and applications be securely configured, but they must be patched/upgraded in a timely fashion.

  4. OWASP-ASVS v4.0.1 V5.3 Output encoding and Injection Prevention Requirements.(5.3.1) Verify that output encoding is relevant for the interpreter and context required. For example, use encoders specifically for HTML values, HTML attributes, JavaScript, URL Parameters, HTTP headers, SMTP, and others as the context requires, especially from untrusted inputs (e.g. names with Unicode or apostrophes, such as ねこ or O’Hara).

  5. OWASP-ASVS v4.0.1 V12.3 File execution Requirements.(12.3.4) Verify that the application protects against reflective file download (RFD) by validating or ignoring user-submitted filenames in a JSON, JSONP, or URL parameter, the response Content-Type header should be set to text/plain, and the Content-Disposition header should have a fixed filename.

  6. OWASP-ASVS v4.0.1 V12.5 File Download Requirements.(12.5.1) Verify that the web tier is configured to serve only files with specific file extensions to prevent unintentional information and source code leakage. For example, backup files (e.g. .bak), temporary working files (e.g. .swp), compressed files (.zip, .tar.gz, etc.) and other extensions commonly used by editors should be blocked unless required.

  7. OWASP-ASVS v4.0.1 V12.5 File Download Requirements.(12.5.2) Verify that direct requests to uploaded files will never be executed as HTML/JavaScript content.

  8. OWASP-ASVS v4.0.1 V13.1 Generic Web Service Security Verification Requirements.(13.1.5) Verify that requests containing unexpected or missing content types are rejected with appropriate headers (HTTP response status 406 Unacceptable or 415 Unsupported Media Type).

  9. OWASP-ASVS v4.0.1 V13.2 RESTful Web Service Verification Requirements.(13.2.5) Verify that REST services explicitly check the incoming Content-Type to be the expected one, such as application/xml or application/JSON.

  10. OWASP-ASVS v4.0.1 V14.4 HTTP Security Headers Requirements.(14.4.1) Verify that every HTTP response contains a content type header specifying a safe character set (e.g., UTF-8, ISO 8859-1).

  11. OWASP-ASVS v4.0.1 V14.4 HTTP Security Headers Requirements.(14.4.2) Verify that all API responses contain Content-Disposition: attachment; filename="api.json" (or other appropriate filename for the content type).

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