A binary backup from Mikrotik, either password-less or your know the password for the backup. You restore the backup to device, but cannot login to webFig/SSH/WinBox/etc.
- Spin RouterOS on a VM (choose Cloud Hosted Router https://mikrotik.com/download), login once, set admin password
- Reboot into live Linux ISO, backup users db from Mikrotik
/rw/store/user.*into/rw/disk/ - Reboot into Mikrotik, restore the backup and reboot. You don't have access to Mikroitk any more.
- Reboot into live Linux ISO, copy users db you backed up on step #2
- Reboot into Mikrotik, use creds from #2