cgi-bin/go in CyberSolutions CyberMail 5 or later allows XSS via the ACTION parameter.
https://www.cybersolutions.co.jp/product/cybermail/
https://www.chtsecurity.com/news/6b907733-c475-4504-b3b7-793442d34335
https://gist.github.com/tonykuo76/d2480727faeb768a97800db3058dceed