The GenerateBlocks plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Dynamic Tag Injection in HTML Attributes in all versions up to, and including, 2.3.0 due to insufficient input sanitization and output escaping. 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. A Contributor-level attacker can store the malicious payload by placing a dynamic tag such as {{post_meta key:...}} in a non-URL HTML attribute (e.g., title, aria-label, alt, or data-* attributes) of a GenerateBlocks element block, then setting the corresponding unprotected post meta key via the Custom Fields metabox to a value containing a closing quote and an injected event-handler attribute.