matthiasnordwig Invisible Anti-Spam & CAPTCHA Plugin up to 5.1 on WordPress admin-ajax.php action cross site scripting

Summaryinfo

A vulnerability was found in matthiasnordwig Invisible Anti-Spam & CAPTCHA Plugin up to 5.1 and classified as problematic. This affects an unknown function of the file admin-ajax.php. The manipulation of the argument action results in cross site scripting. This vulnerability is identified as CVE-2026-16145. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in matthiasnordwig Invisible Anti-Spam & CAPTCHA Plugin up to 5.1. It has been classified as problematic. Affected is an unknown code of the file admin-ajax.php. The manipulation of the argument action with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. This is going to have an impact on integrity. CVE summarizes:

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.

The advisory is shared for download at wordfence.com. This vulnerability is traded as CVE-2026-16145 since 07/17/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

By approaching the search of inurl:admin-ajax.php it is possible to find vulnerable targets with Google Hacking.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• WordPress Plugin

Vendor

• matthiasnordwig

Name

• Invisible Anti-Spam & CAPTCHA Plugin

Version

• 5.0
• 5.1

CPE 2.3info

• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒

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Threat Intelligenceinfo

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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