Why Your Website Gets an F Security Grade (And How to Fix It)

What Does an F Grade Mean?

An F security grade means your website has critical security issues that leave it vulnerable to common attacks. This doesn't necessarily mean your site has been hacked — it means the door is wide open.

The good news is that most F-grade issues are configuration problems that can be fixed in minutes.

Top Reasons for an F Grade

1. No HTTPS / Invalid SSL Certificate

If your site doesn't use HTTPS or has an expired/invalid certificate, that's an automatic F. This is the most critical issue.

Fix:

• Install a free SSL certificate from Let's Encrypt
• Set up auto-renewal so it never expires
• Redirect all HTTP traffic to HTTPS

2. Missing All Security Headers

Having zero security headers is extremely common, especially on sites using default server configs or basic hosting.

Fix: Add at minimum these three headers:

Strict-Transport-Security: max-age=31536000
X-Content-Type-Options: nosniff
X-Frame-Options: DENY

See our complete security headers guide for all recommended headers.

3. Using TLS 1.0 or 1.1

Legacy TLS versions have known vulnerabilities. If your server still supports them, that's a significant security risk.

Fix: Configure your server to only accept TLS 1.2 and 1.3.

4. Insecure Cookies

Session cookies without the Secure, HttpOnly, or SameSite flags are vulnerable to theft and CSRF attacks.

Fix: Set all session cookies with:

Set-Cookie: session=abc123; HttpOnly; Secure; SameSite=Lax; Path=/

5. Server Version Exposed

Headers like Server: Apache/2.4.41 or X-Powered-By: PHP/7.4 tell attackers exactly what software to target.

Fix: Remove or obscure server identification headers. In Nginx:

server_tokens off;

How to Go from F to A

In most cases, you can go from F to A in under 30 minutes:

1. Scan your site and note all failing checks
2. Fix SSL/HTTPS issues first (biggest impact)
3. Add security headers (usually 5 minutes of config)
4. Fix cookie security flags
5. Remove server version exposure
6. Re-scan to verify your fixes

Each step typically improves your grade by one or two letters. The jump from F to A is surprisingly achievable with basic configuration changes.

Prevent Future Grade Drops

Set up scheduled monitoring with WebSentry to automatically re-scan your site daily, weekly, or monthly. You'll be alerted immediately if your grade drops, so you can fix issues before they become exploitable.