CVE-2026-4658 Gutenberg Essential Blocks <= 6.0.4 - Authenticated (Contributor+) Stored Cross-Site Scripting via Block Attributes
Authenticated attackers with Contributor access can inject arbitrary scripts via block attributes, leading to stored XSS execution on victim pages.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-4658?
CVE-2026-4658 is a medium-severity cross-site scripting vulnerability in wpdevteam Gutenberg Essential Blocks – Page Builder for Gutenberg Blocks & Patterns, published on 2 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-4658?
How do I fix CVE-2026-4658?
No fix has been published for CVE-2026-4658 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-4658 being exploited?
There is no known exploitation of CVE-2026-4658 in the wild and no public exploit code.
Sources
Also known as GHSA-5vvh-659m-gjm3.