D-Link GO-RT-AC750 GORTAC750_revA_v101b03 & GO-RT-AC750_revB_FWv200b02 is vulnerable to Static Default Credentials via /etc/init0.d/S80telnetd.sh.
https://www.dlink.com/en/security-bulletin/
https://drive.google.com/file/d/1WNKrDUbYfSWbSve9ONILkLY6dbM8I7hh/view?usp=sharing