D-Link DIR-820LW REVB FIRMWARE PATCH 2.03.B01_TC contains hardcoded credentials in the Telnet service, enabling attackers to log in remotely to the Telnet service and perform arbitrary commands.
https://www.dlink.com/en/security-bulletin/
https://github.com/Nop3z/CVE/blob/main/dlink/dir-820/Dlink-820LW-hardcoded-vulnerability.md