The Page Builder by SiteOrigin plugin for WordPress is vulnerable to Stored Cross-Site Scripting via panels_data Parameter in all versions up to, and including, 2.34.3 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. This is possible because the nonce and edit_post capability checks enforced during save are both satisfied by Contributor-level users for their own posts, and the panels_data value is stored as post meta — outside the scope of WordPress's unfiltered_html carve-out — meaning no wp_kses fallback prevents the unsanitized WP_Widget_Custom_HTML content from being persisted and later rendered verbatim on the frontend.