The Gwolle Guestbook WordPress plugin before 4.2.0 does not sanitise and escape the gwolle_gb_user_email parameter before outputting it back in an attribute, leading to a Reflected Cross-Site Scripting issue in an admin page
XSS exists in admin/gb-dashboard-widget.php in the Gwolle Guestbook (gwolle-gb) plugin before 2.5.4 for WordPress via the PATH_INFO to wp-admin/index.php