Public forms without CAPTCHA: what counts as public

What form CAPTCHA protection is

A CAPTCHA is a challenge in front of a form submission that a script cannot answer cheaply. Modern implementations are usually invisible. reCAPTCHA v3 never interrupts the visitor at all: it returns a score and your server decides what to do with a low one. Cloudflare Turnstile and hCaptcha run a background check and show a challenge only when they need one.

Any form that anyone on the internet can reach and that ends in an email or a database row is a target. Contact forms, comment boxes, newsletter signups and registration forms attract automated submissions within days of going live. A search box or a login form is a different problem: rate limiting and account lockout apply there, not a challenge on every keystroke.

What squirrel checks

The rule runs on every crawled page and emits a single check named form-captcha:

• Info when the page contains no <form> at all. Message: No forms on page.
• Info when no form on the page classifies as public. Message: No public forms detected.
• Warn when at least one public form has no CAPTCHA signal. Message: 2 public form(s) without CAPTCHA, with each form identified by its id, name, action or positional index. Severity warning.
• Pass when every public form is covered. Message: All 2 public form(s) have CAPTCHA.

A form is classified as excluded when it contains an input[type="password"] or when its action, id, class or name contains search, login, signin, sign-in, admin, checkout or cart. It is public when one of those attributes contains contact, comment, feedback, newsletter, subscribe, register, signup, sign-up, inquiry, enquiry, request, support, message or email, or when it holds a <textarea>, or an input[type="email"] with no password field. Anything else is unknown and is not checked.

Protection is detected from the provider scripts, iframes and widget classes of reCAPTCHA, Turnstile, hCaptcha and Friendly Captcha, from their response fields such as g-recaptcha-response, from preload and modulepreload hints pointing at those scripts, from Shopify’s script#captcha-bootstrap bootstrap, and from explicit-render containers whose id or class carries a provider token. FormShield is recognised from a script[src] that either carries a data-fs-project-key attribute or points at formshield.dev or a subdomain of it with a path of /js/formshield.js or /js/formshield.esm.js, and it covers every public form on the page. A page-level signal only credits a public form when that form is the only public form on the page and no other form owns a widget of its own.

How to fix it

<form action="/contact" method="post">
  <textarea name="message"></textarea>
  <div class="cf-turnstile" data-sitekey="0x4AAA..."></div>
  <button type="submit">Send</button>
</form>
<script src="https://challenges.cloudflare.com/turnstile/v0/api.js" async defer></script>

Put the widget inside the form it protects and verify the token server-side before accepting the submission. The client-side widget alone stops nothing.

A form protected by something squirrel cannot see from the HTML, such as a server-side honeypot, a rate limiter or a challenge that only mounts after user interaction, still gets flagged. Disable the rule for that case rather than adding a widget you do not need.

Enable / disable

Disable this rule

[rules]
disable = ["security/form-captcha"]

Disable all Security rules

[rules]
disable = ["security/*"]

Enable only this rule

[rules]
enable = ["security/form-captcha"]
disable = ["*"]

Related rules

• security/form-https: where the same forms submit to.
• a11y/form-labels: whether those fields have accessible names.
• integrity/fake-auth-overlay: login prompts that were never yours.
• security/third-party-cookies: what the challenge provider loads alongside the widget.

Security findings ship in every audit next to the SEO, performance and agent experience rules. See Website security scan with AI for how an agent works through a report.

References

• Automated threats to web applications, OWASP
• The form element, MDN

Check your site

Run squirrel audit https://example.com and open the Security section of the report. Every unprotected public form is listed by page with its selector. Local audits are free.