• Exploit and vulnerability information:  https://www.exploit-db.com/
• Common vulnerabilities and exposures database: https://cve.mitre.org/
• Rapid7 vulnerability and exploit database: https://www.rapid7.com/db
• Nessus scanning tutorials:  https://docs.tenable.com/nessus/Content/Scans.htm
• OpenVAS community forum: https://community.greenbone.net/