wpdevteam Gutenberg Essential Blocks Plugin up to 6.0.4 on WordPress render_callback className/classHook/blockId cross site scripting

Summaryinfo

A vulnerability identified as problematic has been detected in wpdevteam Gutenberg Essential Blocks Plugin up to 6.0.4 on WordPress. This vulnerability affects the function render_callback. The manipulation of the argument className/classHook/blockId leads to cross site scripting. This vulnerability is listed as CVE-2026-4658. The attack may be initiated remotely. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in wpdevteam Gutenberg Essential Blocks Plugin up to 6.0.4 on WordPress. This issue affects the function render_callback. The manipulation of the argument className/classHook/blockId with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. 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. Impacted is integrity. The summary by CVE is:

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.

The weakness was presented by Jack Pas and darkestmode. It is possible to read the advisory at wordfence.com. The identification of this vulnerability is CVE-2026-4658 since 03/23/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 6.0.4 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-26733). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

• WordPress Plugin

Vendor

• wpdevteam

Name

• Gutenberg Essential Blocks Plugin

Version

• 6.0.0
• 6.0.1
• 6.0.2
• 6.0.3
• 6.0.4

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CPE 2.2info

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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