CVE-2026-103424: Anti-Spam by CleanTalk <= 6.88 - Unauthenticated Stored Cross-Site Scripting via Comment Content via ContactsEncoder Greedy Regex
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.
Affected Software
Event History
Frequently Asked Questions
What conditions must an attacker meet to exploit this issue?
The attacker can submit the malicious comment without authentication, but a comment using the attacker’s email address must first be approved. After that approval, subsequent comments from that email address may be automatically approved and can deliver the stored script.
Are default WordPress comment settings affected?
Yes. On default WordPress installations, only the first comment from a given email address is held for moderation, so later comments from that address can auto-approve and immediately expose the payload to visitors.
Who is exposed to the injected script?
Any user who accesses a page containing the injected comment may execute the attacker’s script in their browser. The issue can affect confidentiality and integrity, but no availability impact is identified.