CVE-2026-103424

Anti-Spam by CleanTalk <= 6.88 - Unauthenticated Stored Cross-Site Scripting via Comment Content via ContactsEncoder Greedy Regex

2026-10-09 15:35
Maciej Komorowski

Strategic Overview

Status
Patched in 6.89
Affected Plugin
Spam protection, AntiSpam, FireWall by CleanTalk
Affected Version
<= 6.88
CVSS
5.4Medium
Weakness type
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE
CVE-2026-103424
View all Spam protection, AntiSpam, FireWall by CleanTalk vulnerabilities

At a glance

CVE-2026-103424 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Spam protection, AntiSpam, FireWall by CleanTalk WordPress plugin, affecting versions <= 6.88. It carries a CVSS score of 5.4 (reachable over the network). Exploitation requires no authentication. The issue is fixed in version 6.89; sites on affected versions should update now. Disclosed October 2026, reported by Maciej Komorowski.

Vulnerability Overview

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.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, and no privileges on the target site, and no interaction from a victim user.

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

Spam protection, AntiSpam, FireWall by CleanTalk <= 6.88 carries this weakness at comment, and reaching it takes no account at all. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Spam protection, AntiSpam, FireWall by CleanTalk the fix is 6.89: builds <= 6.88 are affected, anything from 6.89 onward is not.

Remediation

Update to version 6.89, or a newer patched version

How does WordSec protect against this?

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Spam protection, AntiSpam, FireWall by CleanTalk 6.89 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Login Security
  • Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2026-103424https://www.wordfence.com/threat-intel/vulnerabilities/id/c3a80bcd-170b-469b-b090-8f806f87b8d7https://nvd.nist.gov/vuln/detail/CVE-2026-103424

Related records

Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C