Invisible Anti-Spam & CAPTCHA <= 5.1 - Unauthenticated Stored Cross-Site Scripting via 'action' Parameter
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| matthiasnordwig | Invisible Anti-Spam & CAPTCHA — reCAPTCHA Alternative for All Forms | up to 5.1 | — | No fix listed | CNA |
- Invisible Anti-Spam & CAPTCHA — reCAPTCHA Alternative for All Forms Vendormatthiasnordwig Affected up to 5.1 Fixed in — No fix listed CNA
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-16145
- 2026-10-03 Alias added: GHSA-9x6r-qjxj-jj37
References
Other 5
- 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
More matthiasnordwig vulnerabilities
- TI-2026-13512 Invisible Anti-Spam & CAPTCHA <= 5.1 - Authenticated (Editor+) SQL Injection via Pattern JSON Keys/Values CVSS 3.1MEDIUM 4.9
- TI-2026-13472 Invisible Anti-Spam & CAPTCHA <= 5.1 - Authenticated (Editor+) SQL Injection via 'key' Parameter CVSS 3.1MEDIUM 4.9
- TI-2025-31331 Cross-site request forgery in matthiasnordwig Anti-spam, Spam protection, ReCaptcha for… CVSS 3.1MEDIUM 4.3
Sources
- CVE-2026-16145 · CVE Program
- CVE-2026-16145 · NVD
- FIRST EPSS
- GHSA-9x6r-qjxj-jj37 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences