CVE-2026-96840: Post Grid Gutenberg Blocks <= 5.1.0 - Unauthenticated Stored Cross-Site Scripting via display_name User Field
The Post Grid Gutenberg Blocks – PostX plugin for WordPress is vulnerable to Stored Cross-Site Scripting via displayname User Field in all versions up to, and including, 5.1.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. WordPress core's preuserdisplayname filter encodes &, <, and > but leaves double-quotes intact (ENTNOQUOTES), allowing a Subscriber-level user to store a double-quote in their displayname via /wp-admin/profile.php that subsequently breaks out of the alt="" attribute at ArchiveTitle.php:144.
Affected Software
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The attack path requires a WordPress account with Subscriber-level access so the attacker can set a crafted display name through /wp-admin/profile.php. The vulnerable handling allows a double quote in that display name to escape an alt attribute.
When would a malicious payload run?
The payload is stored in the attacker-controlled display name and executes when someone accesses a page that renders the injected content. The affected output is in the plugin's Archive_Title.php template.