CVE-2026-103424: cleantalk anti-spam by cleantalk – spam protection without captcha Cross-site Scripting

Vulnerability summary

CVE-2026-103424 is a medium (CVSS 5.4) Cross-site Scripting vulnerability in cleantalk anti-spam by cleantalk – spam protection without captcha. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 11.9% of scored vulnerabilities. Fixed in 6.89.

Timeline

1. 10-10-2026
   PublishedVulnerability first disclosed.
2. 11-10-2026
   Last modifiedVulnerability information updated.

Description

The Anti-Spam by CleanTalk – Spam Protection Without CAPTCHA plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'comment' parameter in all versions up to, and including, 6.88 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. This vulnerability is exploitable once a comment from the attacker's email address has been approved; on default WordPress installations, only the first comment from a given email address is held for moderation, meaning subsequent comments auto-approve and immediately expose the payload to site visitors.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')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.