ZTE E8820V3 router product is impacted by a permission and access control vulnerability. Attackers could use this vulnerability to tamper with DDNS parameters and send DoS attacks on the specified URL.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2020-28005
http://support.zte.com.cn/support/news/LoopholeInfoDetail.aspx?newsId=1012382