Identification of Security Header Not Set

Identification of missing security headers in web applications is a crucial aspect of penetration testing, as these headers play a significant role in enhancing the security posture of web applications by instructing browsers on how to behave when handling the site's content. Here's how a penetration tester might identify and evaluate the implications of missing security headers:

Steps for Identification

  1. Use Browser Developer Tools: One of the simplest ways to check for security headers is by inspecting the response headers in a browser's developer tools. By navigating to the Network tab and checking the response for each request, a tester can see which headers are included.
  2. Automated Scanning Tools: Tools like OWASP ZAP, Burp Suite, or other specialized tools can automatically scan a web application and report missing security headers. These tools provide a convenient way to scan large applications.
  3. Command-Line Tools: Tools like curl can be used to fetch the headers from the command line. For example, curl -I <> would show the headers received from the server.
  4. Custom Scripts: Writing custom scripts using languages like Python with libraries such as requests can automate the process of checking headers across multiple pages or endpoints.

Common Missing Security Headers

  1. Strict-Transport-Security (HSTS): Ensures that browsers only connect to the website over HTTPS, preventing SSL stripping attacks.
  2. X-Content-Type-Options: Prevents the browser from interpreting files as a different MIME type than what is specified by the content-type header.
  3. X-Frame-Options: Protects against clickjacking attacks by preventing the site from being framed by other sites.
  4. Content-Security-Policy (CSP): Helps prevent cross-site scripting (XSS) and other code injection attacks by specifying which dynamic resources are allowed to load.
  5. X-XSS-Protection: Offers protection against XSS attacks on older browsers that do not support CSP.
  6. Referrer-Policy: Controls the amount of referrer information that should be included with requests.
  7. Feature-Policy: Allows a site to control which features and APIs can be used in the browser.

Implications of Missing Security Headers

  • Increased Vulnerability to XSS: Without CSP or X-XSS-Protection, sites are more susceptible to XSS attacks.
  • SSL Stripping Attacks: Missing HSTS headers can expose users to SSL stripping, where an attacker downgrades a secure HTTPS connection to an insecure HTTP connection.
  • Clickjacking: Without X-Frame-Options, attackers could embed a page within an iframe on a malicious site and trick users into clicking on elements of the invisible page.
  • Data Leakage: Without proper Referrer-Policy, sensitive information could be leaked through HTTP referrer headers.


  • Implement all the relevant security headers based on the specific needs and context of the web application.
  • Regularly audit and test the application to ensure that headers are correctly set and enforced.
  • Keep up-to-date with best practices and emerging standards related to web security headers.

By systematically checking for these headers and understanding their impact, penetration testers can provide valuable insights into the security configuration of web applications, guiding developers and administrators in fortifying their systems against various web-based threats.