X-frames options header cannot be recognized

Nash N Sulthan
Published on
02 May 2024
5 min read

The X-Frame-Options header is a security feature used in web development to mitigate the risks of clickjacking attacks.

Clickjacking, also known as UI redressing, is a technique where an attacker tricks a user into clicking on something different from what the user perceives, potentially leading to unintended actions or unauthorized access.

The X-Frame-Options HTTP response header shows whether a web browser should be permitted to render a webpage in a < frame >, < iframe > or < object >. This header helps to stop clickjacking attacks by ensuring that the content is not embedded into other sites.

This problem may be due to the Per-page policy specification. The reason for this vulnerability might be due to the following:

  • The browser may not support

  • Multiple options may not be supported

  • Nested frames don’t work

What is “X-Frames Options header cannot be recognized” error?

The error message “X-Frame-Options header cannot be recognized” typically indicates an issue with the configuration of the X-Frame-Options header in a web application.

The X-Frame-Options header is a security feature that helps prevent clickjacking attacks.

When the browser receives a response from the server that includes the X-Frame-Options header, it expects a valid directive such as “DENY”, “SAMEORIGIN”, or “ALLOW-FROM uri”. If the header value is not recognized or improperly formatted, the browser may generate this error.


The code below is a useless method to implement X-Frame-Options.

 <meta http-equiv="X-Frame-Options" content="deny">

Impacts of the notification “X-Frame options header cannot be recognized”

1. Security vulnerabilities

Failure to recognize the “X-Frame-Options” header can leave the web application vulnerable to clickjacking attacks.

Without proper framing restrictions, attackers could potentially embed the web page within malicious frames or iframes on other websites, tricking users into performing unintended actions or disclosing sensitive information.

2. Data exposure

If the web page contains sensitive information, such as personal data or confidential documents, its unauthorized embedding in frames or iframes on other sites could result in data exposure.

This could lead to privacy violations or unauthorized access to sensitive information.

3. Phishing and fraud

Attackers may exploit the absence of framing restrictions to create convincing phishing pages.

By embedding legitimate-looking content within malicious frames or iframes, they could deceive users into entering credentials or performing financial transactions on fraudulent websites.

4. Reputation damage

If users encounter unexpected behavior or security warnings due to unrecognized “X-Frame-Options” headers, it could erode trust in the web application or the organization behind it. This can lead to reputational damage and loss of user confidence.

5. Compliance concerns

Failure to implement proper security measures, such as framing restrictions, could result in non-compliance with industry regulations or standards related to data protection and cybersecurity. This may expose the organization to legal liabilities or regulatory penalties.

How can you prevent the notification “X-Frame-Options header cannot be recognized” on your website?

To prevent the issue where the “X-Frame-Options” header cannot be recognized by a web browser, consider the following measures:

1. Proper configuration

Ensure that the “X-Frame-Options” header is correctly configured in your web server’s HTTP response headers. Use one of the valid directives (“DENY”, “SAMEORIGIN”, or “ALLOW-FROM uri”) to specify how the web page should be framed.

2. Header placement

Verify that the “X-Frame-Options” header is placed correctly within the server’s configuration and is sent in the HTTP response headers for all relevant pages.

It should be sent before any content is rendered to ensure proper recognition by web browsers.

3. Header validation

Double-check the spelling, formatting, and syntax of the “X-Frame-Options” header to ensure it complies with the HTTP specification. Any errors or inconsistencies in the header may cause browsers to ignore or misinterpret it.

4. Testing and validation

Regularly test the effectiveness of the “X-Frame-Options” header by using browser developer tools or online security scanning tools. Verify that the header is being correctly recognized and enforced by web browsers across different platforms and versions.

5. Content Security Policy (CSP)

Consider implementing a Content Security Policy (CSP) alongside the “X-Frame-Options” header. CSP provides additional security controls for web content, including framing restrictions, and can complement the protection provided by the “X-Frame-Options” header.

6. Security headers in depth

Explore other security headers, such as “Content-Security-Policy” (CSP) and “X-Content-Type-Options”, to enhance overall web application security.

Implementing a comprehensive set of security headers can help mitigate various types of web security vulnerabilities.

7. Regular updates and maintenance

Stay informed about security best practices and updates related to web server configurations and security headers. Regularly review and update your web server’s configuration to ensure it aligns with the latest security recommendations.

By following these preventive measures, you can help ensure that the “X-Frame-Options” header is correctly recognized and enforced by web browsers, thereby enhancing the security of your web application against clickjacking attacks and other framing-related security risks.

By carefully reviewing your website’s configuration, troubleshooting potential issues, and ensuring that security headers are correctly set and recognized, you can prevent or mitigate the problem of the “X-Frame-Options” header not being recognized and enhance the overall security of your web application.

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Written by
Nash N Sulthan
Nash N Sulthan
Cyber Security Lead Engineer
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