The Grav Form plugin (getgrav/grav-plugin-form) versions 8.0.6 through 9.1.19 select the reCAPTCHA version to validate based solely on which response field key is present in the submitted payload. On a site configured for reCAPTCHA v3, an anonymous attacker can place their v3 token under the v2 field name (g-recaptcha-response instead of token), causing validation to use the v2 branch, which never applies the score threshold or verifies the expected action. This results in a complete bypass of reCAPTCHA v3 bot protection. The issue is fixed in version 9.1.20.

The Grav form plugin (getgrav/grav-plugin-form) before 9.1.13 contains an open redirect vulnerability. Since v9.1.11, the redirect process action evaluates user-supplied form data inside Twig expressions, and Grav::redirect() accepts external URLs without origin validation. When a form blueprint defines a redirect target such as redirect: "{{ form.value('next') }}" using an attacker-controllable field, an unauthenticated form submitter can supply a value like https://evil.com to cause a 302 redirect to an arbitrary external site, enabling phishing.