The Gutenverse – WordPress Blocks, Page Builder & Site Editor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Post Comment Block 'suffixMain' Attribute in all versions up to, and including, 4.0.8 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. WordPress core wp_kses_post sanitization does not mitigate this vulnerability because the payload is stored inside a Gutenberg block delimiter comment rather than as a raw HTML tag, and is only rendered as exploitable HTML at the PHP render stage.