What the vulnerability does
01Description
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.
Explanation of Vulnerability in Simple Terms
02Summary
WPMK Block versions up to 1.0.1 contain a stored cross-site scripting (XSS) vulnerability. An authenticated user with low privileges can inject malicious scripts that execute in the browsers of other site visitors, potentially compromising their sessions or stealing data. The vulnerability affects the entire site scope due to how the block renders user-supplied content.
What an attacker can do
03Attacker Capabilities
Inject malicious scripts that run in other users' browsers when they view affected content.
Potential impact on your site
04Site Impact
Visitors' sessions and data may be compromised if a low-privilege user injects malicious code via the block.
Conditions required to exploit
05Prerequisites
Attacker must have a low-privilege authenticated account on the site.
Key dates
06Disclosure timeline
April 22, 2026
CVE published
April 22, 2026
Record updated
