CVE-2026-4125: The WPMK Block plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'class' shortcode attribute in all versions up to and includi...

Description

The WPMK Block plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'class' shortcode attribute in all versions up to and including 1.0.1. This is due to insufficient input sanitization and output escaping on user-supplied shortcode attributes. Specifically, in the wpmk_block_shortcode() function, the 'class' attribute is extracted from user-controllable shortcode attributes and directly concatenated into an HTML div element's class attribute without any escaping (e.g., esc_attr()). This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

Metrics

CVSS 3.1

6.4/10

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

EPSS Probability

0.29%

20.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

References

Timeline

Published: Apr 22, 2026
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2026-4125?

The WPMK Block plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'class' shortcode attribute in all versions up to and including 1.0.1. This is due to insufficient input sanitization and output escaping on user-supplied shortcode attributes. Specifically, in the wpmk_block_shortcode() function, the 'class' attribute is extracted from user-controllable shortcode attributes and directly concatenated into an HTML div element's class attribute without any escaping (e.g., esc_attr()). This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

How severe is CVE-2026-4125?

CVE-2026-4125 has a CVSS score of 6.4/10 (MEDIUM severity). The EPSS model estimates a 0.29% probability of exploitation in the next 30 days.

How do I fix CVE-2026-4125?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.