# Anti-Spam by CleanTalk <= 6.90 - Unauthenticated Open Redirect via SpamFireWall Block Page

- **ID:** WPSEC-2026-2021
- **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 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
- **Weakness:** CWE-601
- **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-2026-2021/

## Description

The Anti-Spam, Spam FireWall by CleanTalk plugin for WordPress is vulnerable to Open Redirect via the request URI shown on the SpamFireWall block page in all versions up to, and including, 6.90, due to the {REQUEST_URI} link target being escaped only with esc_url(), which keeps protocol-relative values such as '//example.com'. The block page can be shown to any visitor with the 'sfw_test_ip' parameter. This makes it possible for unauthenticated attackers to send users to an external site when they click the 'click to pass' link on a crafted URL.

## References

- https://wpsec.com/vuln/WPSEC-2026-2021/
- 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-2026-2021/

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.