Security header validation in Postman

Introduction

Security header validation helps ensure that web responses include important headers that protect users from attacks. It checks if these headers are present and correctly set.

When testing a website to confirm it uses security headers like Content-Security-Policy or X-Frame-Options.

When verifying that a web API response includes headers to prevent cross-site scripting or clickjacking.

When performing security testing to meet compliance or security standards.

When checking if recent security fixes have been applied to HTTP headers.

When automating tests to catch missing or incorrect security headers in continuous integration.

Syntax

Postman

pm.test('Header Name is present', function () {
    pm.response.to.have.header('Header-Name');
});
pm.test('Header Name has correct value', function () {
    pm.expect(pm.response.headers.get('Header-Name')).to.eql('Expected-Value');
});

Use pm.response.to.have.header() to check if a header exists.

Use pm.expect() with pm.response.headers.get() to check header values.

Examples

This test checks if the Content-Security-Policy header is included in the response.

Postman

pm.test('Content-Security-Policy header is present', function () {
    pm.response.to.have.header('Content-Security-Policy');
});

This test verifies that the X-Frame-Options header is set to DENY, which prevents clickjacking.

Postman

pm.test('X-Frame-Options header has value DENY', function () {
    pm.expect(pm.response.headers.get('X-Frame-Options')).to.eql('DENY');
});

This test confirms the Strict-Transport-Security header contains the max-age directive to enforce HTTPS.

Postman

pm.test('Strict-Transport-Security header includes max-age', function () {
    const sts = pm.response.headers.get('Strict-Transport-Security');
    pm.expect(sts).to.include('max-age');
});

Sample Program

This Postman test script checks three important security headers: Content-Security-Policy, X-Frame-Options, and Strict-Transport-Security. It verifies their presence and correct values to help protect the web application.

Postman

pm.test('Security headers validation', function () {
    pm.response.to.have.header('Content-Security-Policy');
    pm.expect(pm.response.headers.get('Content-Security-Policy')).to.eql("default-src 'self'");

    pm.response.to.have.header('X-Frame-Options');
    pm.expect(pm.response.headers.get('X-Frame-Options')).to.eql('DENY');

    pm.response.to.have.header('Strict-Transport-Security');
    const sts = pm.response.headers.get('Strict-Transport-Security');
    pm.expect(sts).to.include('max-age=31536000');
});

Important Notes

Always check for both presence and correct values of security headers.

Header names are case-insensitive but use the exact spelling for clarity.

Security headers help protect users from common web attacks like XSS and clickjacking.

Summary

Security header validation ensures important HTTP headers exist and have correct values.

Use Postman tests to automate checking headers like Content-Security-Policy and X-Frame-Options.

This helps keep web applications safer and compliant with security best practices.

Practice

1. Which HTTP header is commonly used to prevent clickjacking attacks by controlling if a page can be displayed in a frame or iframe?

easy

A. Strict-Transport-Security

B. Content-Security-Policy

C. X-Frame-Options

D. Cache-Control

Solution

1. Step 1: Understand clickjacking protection

   Clickjacking is prevented by restricting framing of pages.

2. Step 2: Identify the header for frame control

   The X-Frame-Options header controls if a page can be framed.

3. Final Answer:

   X-Frame-Options -> Option C

4. Quick Check:

   Clickjacking protection = X-Frame-Options [OK]

Hint: Remember: Frame control = X-Frame-Options header [OK]

Common Mistakes:

• Confusing Content-Security-Policy with frame control
• Thinking Strict-Transport-Security controls framing
• Ignoring the role of X-Frame-Options

2. Which Postman test script correctly checks if the Content-Security-Policy header exists in the response?

easy

A. pm.test('CSP header present', () => pm.expect(pm.response.headers.get('Content-Security-Policy') !== null).to.be.true);

B. pm.test('CSP header present', () => pm.response.headers.has('content-security-policy') === false);

C. pm.test('CSP header present', () => pm.response.headers.get('Content-Security-Policy') === undefined);

D. pm.test('CSP header present', () => pm.response.headers.has('Content-Security-Policy'));

Solution

1. Step 1: Understand Postman header methods

   pm.response.headers.get() returns the header value or null if missing.

2. Step 2: Check for header existence correctly

   Checking if the value is not null confirms header presence.

3. Final Answer:

   pm.test('CSP header present', () => pm.expect(pm.response.headers.get('Content-Security-Policy') !== null).to.be.true); -> Option A

4. Quick Check:

   Header exists if get() !== null [OK]

Hint: Use get() !== null to check header presence [OK]

Common Mistakes:

• Using headers.has() which returns boolean but not tested properly
• Checking for undefined instead of null
• Negating the condition incorrectly

3. Given this Postman test code, what will be the test result if the response header X-Content-Type-Options is missing?

pm.test('X-Content-Type-Options header is set', () => {
  pm.response.to.have.header('X-Content-Type-Options');
});

medium

A. Test passes because header check is optional

B. Test passes but logs a warning

C. Test throws a syntax error

D. Test fails because header is missing

Solution

1. Step 1: Understand the assertion used

   pm.response.to.have.header() asserts the header must exist.

2. Step 2: Analyze missing header effect

   If the header is missing, the assertion fails and test fails.

3. Final Answer:

   Test fails because header is missing -> Option D

4. Quick Check:

   Missing required header = test failure [OK]

Hint: Required header missing causes test failure [OK]

Common Mistakes:

• Assuming test passes if header is missing
• Confusing syntax error with assertion failure
• Thinking warnings are logged instead of failure

4. Identify the error in this Postman test script that checks if the Strict-Transport-Security header includes max-age=31536000:

pm.test('HSTS max-age check', () => {
  pm.expect(pm.response.headers.get('Strict-Transport-Security')).to.include('max-age=31536000');
});

medium

A. Not checking if header exists before calling get()

B. Using to.include instead of to.have.string

C. Incorrect header name casing

D. Missing semicolon after pm.test

Solution

1. Step 1: Understand get() behavior when header missing

   If header is missing, get() returns null, causing error on to.include.

2. Step 2: Identify missing existence check

   Test should first check header exists before checking content.

3. Final Answer:

   Not checking if header exists before calling get() -> Option A

4. Quick Check:

   Check header presence before content check [OK]

Hint: Always verify header exists before content assertions [OK]

Common Mistakes:

• Assuming get() never returns null
• Ignoring null causing test errors
• Focusing on casing or semicolons instead

5. You want to write a Postman test to ensure the Content-Security-Policy header disallows inline scripts by including script-src 'self'. Which test script correctly validates this?

hard

A. pm.test('CSP disallows inline scripts', () => {
pm.expect(pm.response.headers.get('Content-Security-Policy')).to.equal("script-src 'self'");
});

B. pm.test('CSP disallows inline scripts', () => {
const csp = pm.response.headers.get('Content-Security-Policy');
pm.expect(csp).to.include("script-src 'self'");
});

C. pm.test('CSP disallows inline scripts', () => {
pm.expect(pm.response.headers.has('Content-Security-Policy')).to.be.true;
});

D. pm.test('CSP disallows inline scripts', () => {
pm.expect(pm.response.headers.get('Content-Security-Policy')).to.include('unsafe-inline');
});

Solution

1. Step 1: Understand CSP header content

   The header can contain multiple directives; we check if it includes script-src 'self'.

2. Step 2: Validate correct assertion method

   Using to.include checks if the string contains the directive, allowing other parts.

3. Final Answer:

   pm.test('CSP disallows inline scripts', () => { const csp = pm.response.headers.get('Content-Security-Policy'); pm.expect(csp).to.include("script-src 'self'"); }); -> Option B

4. Quick Check:

   Use include() to check partial CSP directive [OK]

Hint: Use include() to check CSP directives inside header string [OK]

Common Mistakes:

• Using to.equal which requires exact match
• Only checking header presence without content
• Checking for 'unsafe-inline' which allows inline scripts