CVE-2026-4658: wordpress essential-blocks Cross-site Scripting

Vulnerability summary

CVE-2026-4658 is a medium (CVSS 6.4) Cross-site Scripting vulnerability in wordpress essential-blocks. EPSS estimates a 0.42% chance of exploitation in the next 30 days, higher than 34.7% of scored vulnerabilities. Fixed in 6.1.0.

Timeline

1. 02-05-2026
   PublishedVulnerability first disclosed.
2. 04-05-2026
   Last modifiedVulnerability information updated.

Description

The Essential Blocks – Page Builder Gutenberg Blocks, Patterns & Templates plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the className, classHook, and blockId attributes in the Add to Cart block (essential-blocks/add-to-cart) in all versions up to, and including, 6.0.4. This is due to insufficient output escaping in the render_callback() function where these attributes are placed into class and data-id HTML attributes using raw sprintf() and implode() without esc_attr() escaping. While the outer wrapper div uses get_block_wrapper_attributes() which properly escapes, the inner divs do not. 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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.