CVE-2026-17577: XSS (CVSS 6.1)

Description

The SSL Zen plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'uri' (and 'host') parameters in versions up to, and including, 4.7.42. The ssl_zen_messages::getMessages() function builds the 'token_missmatch' message using base64_decode(sanitize_text_field($_REQUEST['uri'])) and (optionally) base64_decode(sanitize_text_field($_REQUEST['host'])). sanitize_text_field() cannot strip HTML/JavaScript that is hidden inside a base64-encoded blob, and the resulting decoded raw HTML is echoed unescaped by showMessage() . This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a specially crafted link.

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CVSS v3.1 Score

6.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.18%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

References

Other References

https://plugins.trac.wordpress.org/browser/ssl-zen/tags/4.7.14/ssl_zen/classes/class.ssl_zen_admin.php#L863 https://plugins.trac.wordpress.org/browser/ssl-zen/tags/4.7.14/ssl_zen/classes/class.ssl_zen_messages.php#L44 https://plugins.trac.wordpress.org/browser/ssl-zen/tags/4.7.42/ssl_zen/classes/class.ssl_zen_admin.php#L863 https://plugins.trac.wordpress.org/browser/ssl-zen/tags/4.7.42/ssl_zen/classes/class.ssl_zen_messages.php#L44 https://plugins.trac.wordpress.org/changeset?reponame=&old=3701590%40ssl-zen&new=3701590%40ssl-zen https://www.wordfence.com/threat-intel/vulnerabilities/id/20816039-0b1c-420a-b5f4-b5370d0331da?source=cve

Frequently Asked Questions

What is CVE-2026-17577? +

The SSL Zen plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'uri' (and 'host') parameters in versions up to, and including, 4.7.42. The ssl_zen_messages::getMessages() function builds the 'token_missmatch' message using base64_decode(sanitize_text_field($_REQUEST['uri'])) and (optionally) base64_decode(sanitize_text_field($_REQUEST['host'])). sanitize_text_field() cannot strip HTML/JavaScript that is hidden inside a base64-encoded blob, and the resulting decoded raw HTML is echoed unescaped by showMessage() . This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a specially crafted link. It has a CVSS v3.1 base score of 6.1 (MEDIUM).

How severe is CVE-2026-17577? +

CVE-2026-17577 has a CVSS v3.1 score of 6.1 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-17577? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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