The Easy Accordion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'accordionTitleTag' block attribute in versions up to, and including, 3.1.8. This is due to insufficient input sanitization and output escaping in the accordion_header_renderer() function, which emits the attacker-supplied tag name using esc_attr() in an HTML tag-name context instead of tag_escape(). 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.