A Security Headers Checklist for AI-Built Apps

Quick answer: A security headers checklist for 2026 must include Content-Security-Policy (CSP), HSTS with preloading, X-Content-Type-Options, X-Frame-Options, and Referrer-Policy. These headers prevent XSS, clickjacking, and data leaks. SimplyScan's data shows 33% of AI-built apps have high-severity issues, often due to missing these essential browser-level protections.

By Gabriel CA · Kraftwire Software

Web applications built using AI tools like Lovable, Bolt.new, or Cursor often prioritize rapid feature delivery over infrastructure hardening. While these platforms generate functional code, they frequently omit the HTTP response headers required to protect users from modern browser-based attacks. A security headers checklist is the first line of defense against cross-site scripting (XSS), clickjacking, and protocol downgrades.

In SimplyScan's scans of 177 AI-built apps, 58 of those apps (33%) had at least one HIGH or CRITICAL severity issue. Many of these vulnerabilities stem from missing security headers that would otherwise neutralize common exploit vectors. Implementing these headers does not require changing your application logic · it only requires a few lines of configuration in your deployment platform or middleware.

Why Do AI-Built Apps Need A Security Headers Checklist?

AI-driven development, or vibe-coding, often relies on the default configurations of hosting providers like Vercel, Netlify, or Replit. While these platforms provide basic protection, they cannot guess your application's specific security requirements. For example, an AI might generate a frontend that calls an external API but fail to configure a Content Security Policy (CSP) that restricts which domains the browser is allowed to contact.

Without these headers, your app is vulnerable to:

• Session Hijacking: If HSTS is missing, attackers can downgrade a user's connection to unencrypted HTTP.
• Data Exfiltration: Without a CSP, an injected script can send sensitive user data to a malicious server.
• Clickjacking: If your app can be loaded in an iframe on a third-party site, attackers can trick users into performing unintended actions.

What Is The Content Security Policy (CSP) Requirement?

The Content Security Policy is the most powerful header in your arsenal. It tells the browser exactly which scripts, styles, and images are trusted. It is often the most difficult header to configure because a strict policy can break third-party integrations if not tested thoroughly.

For AI-built apps, a "Strict CSP" is recommended. This avoids the use of unsafe-inline and instead uses nonces or hashes to validate scripts.

Recommended CSP Configuration

This policy does the following:

• default-src 'self': Only allows content from your own domain.
• script-src 'self': Prevents the execution of inline scripts and scripts from external domains.
• object-src 'none': Disables plugins like Flash.
• frame-ancestors 'none': Prevents other sites from embedding your app in an iframe.

If you are using a platform like Lovable, you should verify your CSP settings to ensure they don't block necessary assets. You can learn more in our Lovable security guide.

How To Implement Strict Transport Security (HSTS)?

HTTP Strict Transport Security (HSTS) ensures that a browser only communicates with your server over a secure HTTPS connection. Even if a user types http:// in their browser, HSTS forces an internal redirect to https:// before any data is sent over the wire.

Many developers fail to include the preload directive, which is necessary to protect the very first visit to a site. Without preloading, the initial request remains vulnerable to interception.

Recommended HSTS Configuration

The max-age of 63072000 seconds (two years) is the current industry recommendation for production environments. Before applying this, ensure your SSL certificate is valid and correctly configured using an SSL checker.

Is X-Frame-Options Still Necessary?

While the frame-ancestors directive in CSP has largely superseded X-Frame-Options, it is still considered best practice to include both for compatibility with older browsers. This header prevents clickjacking by instructing the browser whether it is allowed to render your page in a <frame>, <iframe>, <embed>, or <object>.

Recommended X-Frame-Options Configuration

Using DENY is the safest choice for most AI-built SaaS applications. If you specifically need to allow your app to be embedded on your own subdomains, use SAMEORIGIN. For more complex architectural needs, review our guide on architecture security risks.

What Does X-Content-Type-Options Do?

This header is a simple but effective "opt-in" for a security feature in the browser. It prevents the browser from "sniffing" the MIME type of a response. Without this header, a browser might try to interpret a plain text file as JavaScript if it looks like code, leading to XSS vulnerabilities.

Recommended X-Content-Type-Options Configuration

This is a "set and forget" header that should be applied to every single web application. It is one of the easiest wins in any application security checklist.

How Should Referrer-Policy Be Configured?

When a user clicks a link on your site that leads to another website, the browser typically sends the URL of your page in the Referer header. This can accidentally leak sensitive information, such as tokens or user IDs contained in your URL structure.

Recommended Referrer-Policy Configuration

This setting sends the full URL when navigating within your own site but only sends the domain (the origin) when navigating to a different site. This protects user privacy while maintaining the utility of analytics.

What Is The Permissions-Policy Header?

Formerly known as Feature-Policy, the Permissions-Policy header allows you to explicitly disable browser features that your app doesn't use, such as the camera, microphone, or geolocation. This limits the "blast radius" if an attacker manages to inject a script into your page.

Recommended Permissions-Policy Configuration

By setting these to empty parentheses, you ensure that even if a vulnerability exists, an attacker cannot use the browser to spy on your users.

How To Audit Your Headers Automatically?

Manually checking headers for every deployment is prone to error, especially when using "vibe-coded" workflows where code changes rapidly. In SimplyScan's scans of 177 AI-built apps, security issues (high) appeared in 19 apps (11%). Many of these could have been caught instantly with automated scanning.

SimplyScan provides a free site health scanner designed specifically for AI-built apps. In about 30 seconds, it grades your security headers along with seven other dimensions:

• Security: Detects missing headers, exposed API keys, and Supabase RLS issues.
• Speed: Identifies performance bottlenecks (speed issues appeared in 70% of scanned apps).
• Compliance: Checks for GDPR signals and email security records like SPF, DKIM, and DMARC.

You can run a free scan at SimplyScan.io to see your current security grade and get a specific checklist of which headers are missing from your configuration.

Summary Checklist For Production Apps

Before you consider your AI-built app "production-ready," verify that your server or hosting provider is sending these five essential headers:

• Content-Security-Policy: Restrict script sources and disable unsafe-inline.
• Strict-Transport-Security: Force HTTPS with a long max-age and preload.
• X-Content-Type-Options: Set to nosniff to prevent MIME-type sniffing.
• X-Frame-Options: Set to DENY or SAMEORIGIN to stop clickjacking.
• Referrer-Policy: Set to strict-origin-when-cross-origin to protect privacy.

For developers using specialized backends, ensure you also follow platform-specific advice, such as the Supabase security checklist or the Firebase security checklist. Properly configured headers are a low-effort, high-impact way to ensure your "vibe" stays secure.