The Redux Framework plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the spinner field in versions up to, and including, 4.5.13 This is due to insufficient input sanitization and output escaping. In the user_meta_save() function scalar values bypass the sanitization logic that only processes arrays, allowing the spinner field value to be stored in user meta without proper sanitization. Later, at line 56 of class-redux-spinner.php in the render() function, this value is rendered in an unquoted HTML attribute without escaping via '$data_string .= ' data-val=' . $this->value;'. This makes it possible for authenticated attackers, with subscriber-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.