Mail.ru: [delivery.city-mobil.ru] Stored XSS into support request comment

Stored XSS in support request comment functionality on delivery.city-mobil.ru Citymobil corporate user could use delivery.city-mobil.ru API for submitting data. It led to bypass input-encoding filters of corporate.city-mobil.ru and stored XSS appeared at corporate.city-mobil.ru...