The plugin does not sanitise and escape its settings, allowing high privilege users such as admin to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed
Put the following payload in any of textarea field settings of the plugin (such as 'Google Analytics'): "><svg onload=alert(/XSS/)>
The XSS will be triggered when accessing the Theme Customizer page (/wp-admin/customize.php)