Cookie Security & Flag Audit
Audit Set-Cookie HTTP headers for Secure, HttpOnly, SameSite, and RFC 6265bis prefix compliance with real-time security scoring.
Set-Cookie Security Inspector
Secure; HttpOnly; SameSite=Strict
Set-Cookie: headers or raw semicolon-separated strings.Cookies Parsed: 1session_idSecurity Findings & Audit Checks
This cookie appears to carry authentication or session data but lacks the "Secure" directive, allowing it to be transmitted over unencrypted HTTP.
Authentication token or session cookie is accessible to JavaScript document.cookie, making it vulnerable to Cross-Site Scripting (XSS) exfiltration.
Modern browsers default unspecified cookies to Lax, but explicit declaration prevents ambiguity across legacy clients and cross-site requests.
Domain attribute is set to ".example.com", making the cookie accessible to all subdomains of this root.
Set-Cookie: session_id=abc123xyz890; Path=/; Domain=.example.com; Max-Age=2592000; Secure; HttpOnly; SameSite=Lax
In-Browser RFC 6265 & RFC 6265bis HTTP Cookie Security and Flag Auditing
The Cookie Audit Tool evaluates HTTP Set-Cookie response headers and browser cookie strings for security compliance, cross-site request forgery (CSRF) defenses, and cross-site scripting (XSS) resilience. Running locally inside your browser, it analyzes cookie attributes against modern RFC 6265 and RFC 6265bis specifications without routing sensitive session identifiers through third-party servers.
The auditor checks for essential security flags, including the Secure directive (ensuring transmission exclusively over encrypted TLS connections), the HttpOnly flag (preventing client-side JavaScript access via document.cookie), and explicit SameSite enforcement (Strict, Lax, or None). It also audits strict cookie prefixes (__Host- and __Secure-) and validates maximum lifetime constraints against the modern 400-day browser expiration cap.
System administrators, web developers, and penetration testers receive an automated 0-to-100 security health score, letter grade (A+ through F), categorized vulnerability findings with remediation instructions, and an auto-generated hardened Set-Cookie snippet.
Core Tool Capabilities
- Comprehensive Directive Flag Inspection: Audits Secure, HttpOnly, SameSite, Path, Domain, and Max-Age/Expires attributes to prevent session hijacking and token exfiltration.
- RFC 6265bis Prefix Validation: Validates __Host- and __Secure- cookie prefixes, verifying that __Host- cookies enforce Path=/, Secure, and omit Domain attributes.
- Deterministic Security Scoring and Grading: Computes a weighted security grade from A+ (fully hardened) to F (vulnerable authentication cookie) based on OWASP security benchmarks.
- Multi-Cookie Header Parsing: Parses multiple Set-Cookie headers or semicolon-separated document.cookie strings simultaneously with aggregated summary statistics.
- Hardened Header Code Generator: Provides a reconstructed, RFC-compliant Set-Cookie header snippet with recommended security directives ready to copy into web server configs.
Local Browser Privacy
Your files are processed locally on your device. Files are not uploaded, transmitted, or stored on remote servers.
Once the page has loaded, you can disconnect your network connection and continue using this tool offline.
Target Use Cases
- • Web Application Security Auditing
- • Backend API Response Verification
- • RFC 6265bis Prefix Migration
- • Third-Party Integration Troubleshooting
Technical Specifications & Platform Limits
Official IETF HTTP State Management and Web Application Security standards.
Full suite of standard and modern browser cookie attributes.
Rigorous RFC 6265bis origin-bound cookie prefix rules.
Zero external network requests or cookie logging.
Step-by-Step Workflow
Enter Set-Cookie Headers or Cookie String
Paste one or more Set-Cookie HTTP response headers or a document.cookie string into the input workspace.
Inspect Overall Security Posture
Review the overall security score, grade badge, and summary counters for Secure, HttpOnly, SameSite, and critical issues.
Examine Individual Findings
Explore detailed check results for each parsed cookie, reviewing specific risk descriptions and actionable remediation advice.
Copy Hardened Set-Cookie Snippet
Copy the recommended hardened Set-Cookie header to apply secure configurations in Nginx, Apache, Express, or Cloudflare.
Practical Real-World Use Cases
Web Application Security Auditing
Penetration testers and security engineers verifying that session cookies and JWT auth tokens are properly protected against XSS and CSRF.
Backend API Response Verification
Backend developers testing authentication microservices to confirm that Set-Cookie headers contain necessary security flags before deploying to production.
RFC 6265bis Prefix Migration
DevOps teams adopting __Host- cookie prefixes to protect sensitive session cookies from subdomain takeover and domain scoping attacks.
Third-Party Integration Troubleshooting
Frontend engineers troubleshooting iframe embedding and cross-site widget cookies rejected due to missing SameSite=None; Secure directives.
Frequently Asked Questions
- Why is the HttpOnly flag critical for session cookies?
- The HttpOnly flag blocks client-side scripts from reading the cookie through document.cookie. If an attacker discovers a Cross-Site Scripting (XSS) vulnerability on your site, HttpOnly prevents them from directly stealing the user's session token via JavaScript.
- What is the difference between SameSite=Strict and SameSite=Lax?
- SameSite=Strict prevents the cookie from being sent on any cross-site request, including top-level links followed from external sites. SameSite=Lax permits the cookie to be sent on top-level GET navigations (such as clicking an external link) while blocking cross-site POST requests, offering a balance between security and user convenience.
- Why do modern browsers reject SameSite=None cookies without the Secure flag?
- Under RFC 6265bis, any cookie configured with SameSite=None is designated for cross-site usage and must be transmitted exclusively over encrypted HTTPS connections. Browsers automatically drop SameSite=None cookies that lack the Secure directive.
- What requirements must a __Host- cookie satisfy?
- A cookie using the __Host- prefix must have the Secure flag enabled, must have Path set to exactly '/', and must NOT declare a Domain attribute. This binds the cookie strictly to the originating host and prevents subdomains from reading or overriding it.
- Are my cookie strings or session tokens stored or logged?
- No. All parsing and audit rule evaluations execute entirely within your client browser session. No session tokens, headers, or cookie values are transmitted to any server.
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Master this tool with Guides & Articles
Learn the workflows, common mistakes, and advanced techniques behind Cookie Security Auditor - Check Cookie Flags, SameSite, and Security with our deep-dive educational content.