An issue was discovered on D-Link DSR-250 3.17 devices. Insufficient validation of configuration file checksums could allow a remote, authenticated attacker to inject arbitrary crontab entries into saved configurations before uploading. These entries are executed as root.
https://www.dlink.com/en/security-bulletin
https://www.digitaldefense.com/news/zero-day-vuln-d-link-vpn-routers/
https://supportannouncement.us.dlink.com/announcement/publication.aspx?name=SAP10195