Security Headers Scanner: Check Missing HTTP Headers Before They Become Security Gaps

Security headers are small lines of configuration that can make a major difference to website security.

They tell the browser how to behave when loading your website, handling scripts, embedding content, enforcing HTTPS, sharing referrer data, and protecting users from browser-based attacks.

Security headers are often the first layer of browser-side defense, but they are also one of the easiest controls to miss. Com Olho’s online vulnerability scanner helps check website-level security gaps, including missing or weak HTTP security headers such as CSP, HSTS, X-Frame-Options, Referrer-Policy, and related hardening controls.

A security headers scanner checks whether your website has the right HTTP response headers configured correctly.

It helps answer questions like:

• Can your website be embedded inside another website?

• Is HTTPS enforced properly?

• Can browsers load scripts from unsafe sources?

• Are cookies protected?

• Is sensitive referrer information leaking?

• Are browser permissions restricted?

• Are your headers present but misconfigured?
  

Security headers do not replace secure coding. But without them, the browser loses important instructions that reduce the impact of attacks like clickjacking, cross-site scripting, MIME sniffing, and insecure transport behavior.

What Is a Security Headers Scanner?

A security headers scanner is a tool that analyzes the HTTP response headers of a website and identifies missing, weak, or misconfigured security headers.

When a browser requests a website, the server responds with content and headers. These headers define how the browser should handle that content.

A scanner checks whether headers such as the following are present and properly configured:

• Content-Security-Policy

• Strict-Transport-Security

• X-Frame-Options

• X-Content-Type-Options

• Referrer-Policy

• Permissions-Policy

• Cache-Control

• Set-Cookie attributes

  
  

In simple terms:

A security headers scanner checks whether your website is giving the browser the right security instructions.

Why Security Headers Matter

Modern attacks do not always start with a server compromise.

Sometimes attackers exploit how browsers load content, execute scripts, display pages, or share data between origins

.

Security headers help reduce this risk.

For example, X-Frame-Options can help prevent a website from being rendered inside a malicious frame or iframe. This is useful for reducing clickjacking exposure, where a user may be tricked into clicking a hidden or disguised interface element.

Without proper headers, even a well-built website may expose users to avoidable browser-side risks.

Key Security Headers Every Website Should Check

1. Content-Security-Policy

Content-Security-Policy, commonly called CSP, helps control which sources are allowed to load scripts, styles, images, frames, fonts, and other resources.

A strong CSP can reduce the impact of cross-site scripting and unauthorized script execution.

A security headers scanner should check:

• Whether CSP exists

• Whether unsafe directives are present

• Whether wildcard sources are used

• Whether inline scripts are allowed

• Whether third-party domains are controlled

• Whether reporting is enabled

Example risk:

A website loads scripts from unrestricted third-party sources. If one third-party script is compromised, attackers may be able to execute malicious JavaScript in the user’s browser.

2. Strict-Transport-Security

Strict-Transport-Security, or HSTS, tells browsers to access the website only over HTTPS for a defined period.

This helps reduce downgrade and protocol-stripping risks.

A scanner should check:

• Whether HSTS is enabled

• Whether max-age is sufficient

• Whether subdomains are included

• Whether preload readiness is appropriate

Example risk:

A user types the website address manually, and the browser initially attempts HTTP. Without HSTS, attackers on the network may attempt downgrade-based attacks.

3. X-Frame-Options

X-Frame-Options helps prevent a website from being loaded inside a frame on another website.

This is important for preventing clickjacking attacks, where users are tricked into clicking hidden or disguised interface elements.

A scanner should check whether the value is:

• DENY

• SAMEORIGIN

For modern applications, CSP’s frame-ancestors directive can also be used for more flexible frame control.

4. X-Content-Type-Options

X-Content-Type-Options helps stop browsers from MIME-sniffing a response away from the declared content type.

The recommended value is usually:

nosniff

Example risk:

A file uploaded as text may be interpreted as executable script by the browser if MIME sniffing is allowed.

5. Referrer-Policy

Referrer-Policy controls how much referrer information is sent when users navigate from your website to another destination.

A scanner should check whether the policy limits unnecessary exposure of full URLs, query strings, or sensitive path information.

Common safer values include:

• strict-origin-when-cross-origin

• no-referrer

• same-origin

Example risk:

A password reset URL, tokenized link, internal path, or user-specific query string may leak to third-party domains through referrer headers.

6. Permissions-Policy

Permissions-Policy controls which browser features can be used by your website or embedded frames.

It can restrict access to:

• Camera

• Microphone

• Geolocation

• Payment

• USB

• Clipboard

• Fullscreen

• Accelerometer

Example risk:

A compromised third-party frame may attempt to access sensitive browser capabilities if permissions are not restricted.

7. Cookie Security Attributes

While not always grouped under “security headers,” cookie attributes are critical.

A scanner should check whether cookies use:

• Secure

• HttpOnly

• SameSite

• Proper domain scoping

• Appropriate expiry

• No sensitive data in cookie values

Example risk:

A session cookie without HttpOnly may be easier to steal through client-side script execution.

What a Security Headers Scanner Should Report

A useful security headers scanner should not only say “pass” or “fail.”

It should explain:

Scanner Output	Why It Matters
Missing header	Shows absent browser protection
Weak value	Header exists but does not provide strong protection
Misconfigured directive	Header may break security expectations
Risk description	Helps non-technical teams understand impact
Recommended value	Gives developers a fix direction
Compatibility note	Reduces risk of breaking production behavior
Retest option	Confirms whether remediation worked

Security Headers Scanner Example Findings

A scan may identify findings like:

Missing Content-Security-Policy

The website does not define a CSP header. This increases the potential impact of cross-site scripting and unauthorized resource loading.

Missing HSTS

The website does not enforce HTTPS through HSTS. Users may be exposed to downgrade or insecure transport behavior in certain network conditions.

X-Frame-Options Missing

The website may be embedded into malicious pages, increasing clickjacking risk.

Referrer-Policy Not Set

Sensitive path or query information may be shared with third-party websites when users navigate away.

Cookies Missing Secure Attribute

Cookies may be transmitted over insecure channels if HTTP is available.

Security Headers Scanner vs Website Vulnerability Scanner

A security headers scanner is more focused. A website vulnerability scanner is broader.

Capability	Security Headers Scanner	Website Vulnerability Scanner
Checks HTTP headers	Yes	Yes
Finds missing CSP/HSTS	Yes	Yes
Detects exposed files	No	Yes
Tests input fields	No	Yes
Crawls website paths	Limited	Yes
Checks outdated components	Limited	Yes
Tests authentication flows	No	Yes
Best use	Browser-side hardening	Full website security visibility

A security headers scanner is ideal for quick hardening checks. But it should be part of a wider website security program.

Why Missing Security Headers Are Often Ignored

Security headers are frequently missed because they sit between development, infrastructure, DevOps, and security.

Developers may assume DevOps configured them.DevOps may assume the application framework handles them.Security teams may find them during audits but not track closure continuously.

This creates a gap.

A missing header may not look as severe as SQL injection or account takeover, but it weakens browser-side defense. In chained attacks, these missing protections can increase real-world impact.

How Com Olho Helps With Security Header Visibility

Com Olho helps organizations identify missing and weak security headers as part of broader continuous vulnerability assessment.

Instead of treating headers as isolated checklist items, Com Olho helps connect them to real attack surface context:

• Which website or subdomain is affected?

• Is it production-facing?

• Does it handle login or sensitive workflows?

• Is it part of a larger application?

• Can the issue increase the impact of another vulnerability?

• Has the fix been validated?

This makes header scanning more useful for security teams, developers, and leadership.

Header	Recommended Purpose
Content-Security-Policy	Restrict resource loading and script execution
Strict-Transport-Security	Enforce HTTPS
X-Frame-Options	Reduce clickjacking risk
X-Content-Type-Options	Prevent MIME sniffing
Referrer-Policy	Limit referrer leakage
Permissions-Policy	Restrict browser feature access
Cache-Control	Prevent sensitive data caching
Set-Cookie: Secure	Send cookies only over HTTPS
Set-Cookie: HttpOnly	Restrict JavaScript access to cookies
Set-Cookie: SameSite	Reduce cross-site request risk

Final Thoughts

A security headers scanner is one of the fastest ways to improve website hardening.

It does not require deep application access. It does not need source code. It can be run frequently. It gives immediate visibility into browser-side security posture.

But the real value comes when header scanning is connected to continuous vulnerability management, ownership, remediation, and retesting.

Security headers are small controls.The risk of ignoring them is not small.

FAQ

What is a security headers scanner?

A security headers scanner checks whether a website has important HTTP security headers such as CSP, HSTS, X-Frame-Options, Referrer-Policy, and Permissions-Policy configured correctly.

Why are security headers important?

Security headers help browsers enforce safer behavior. They can reduce risks related to clickjacking, cross-site scripting impact, insecure transport, MIME sniffing, and sensitive referrer leakage.

Is missing CSP a vulnerability?

Missing CSP is usually considered a security weakness or hardening gap. Its severity depends on the application context, exposure, and whether it can increase the impact of other vulnerabilities.

What is the most important security header?

There is no single universal answer. For most websites, CSP, HSTS, X-Frame-Options or CSP frame-ancestors, X-Content-Type-Options, Referrer-Policy, and secure cookie attributes are important.

Can security headers break a website?

Yes. Headers like CSP can break scripts, images, styles, or third-party integrations if configured without testing. Changes should be deployed carefully and validated.

Strengthen your browser-side security posture before small configuration gaps become exploitable attack paths. Use Com Olho to continuously assess website security headers, exposed assets, and web-facing risks. Scan your Security Headers now