# Anti-Spam by CleanTalk <= 6.90 - Unauthenticated Contacts Encoder Bypass via Public Pass Key

- **ID:** WPSEC-2026-2023
- **Plugin:** Anti-Spam, Spam FireWall by CleanTalk (`cleantalk-spam-protect`), https://wordpress.org/plugins/cleantalk-spam-protect/
- **Affected versions:** all versions before 6.91
- **Fixed in:** 6.91 (Update to 6.91 or later.)
- **Severity:** Medium 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
- **Weakness:** CWE-565
- **Usage among sites WPSec scans:** plugin High, affected versions High (as of 2026-10-30)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/cleantalk-spam-protect
- **Fix released:** 2026-10-29
- **Published:** 2026-10-30
- **URL:** https://wpsec.com/vuln/WPSEC-2026-2023/

## Description

The Anti-Spam, Spam FireWall by CleanTalk plugin for WordPress is vulnerable to a Protection Mechanism Bypass via the Contacts Encoder in all versions up to, and including, 6.90. This is due to the 'apbct_email_encoder_passed' cookie being compared against a pass key that the plugin prints to every visitor. This makes it possible for unauthenticated attackers to have e-mail addresses and phone numbers protected by the Contacts Encoder shown unencoded.

## References

- https://wpsec.com/vuln/WPSEC-2026-2023/
- https://plugins.svn.wordpress.org/cleantalk-spam-protect/tags/6.91/
- https://wordpress.org/plugins/cleantalk-spam-protect/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-2023/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to use, share and adapt, also commercially, if you credit WPSec and link to this advisory.