FTP Unencrypted Cleartext Login is the vulnerability that may affect the website according to the severity factor in the above scenario. A vulnerability is a weakness or flaw in a system or network that can be exploited by an attacker to compromise its security or functionality. A vulnerability assessment is a process that involves identifying, analyzing, and evaluating vulnerabilities in a system or network using various tools and techniques. Greenbone is a tool that can perform vulnerability assessment on various targets using various tests and scans. To perform a vulnerability assessment on the given IP address 20.20.10.26, one has to follow these steps:
Open a web browser and type 20.20.10.26:9392
Press Enter key to access the Greenbone web interface.
Enter admin as username and password as password.
Click on Login button.
Click on Scans menu and select Tasks option.
Click on Start Scan icon next to IP Address Scan task.
Wait for the scan to complete and click on Report icon next to IP Address Scan task.
Observe the vulnerabilities found by the scan.
The vulnerabilities found by the scan are:

The vulnerability that may affect the website according to the severity factor is FTP Unencrypted Cleartext Login, which has a medium severity level. FTP Unencrypted Cleartext Login is a vulnerability that allows an attacker to intercept or sniff FTP login credentials that are sent in cleartext over an unencrypted connection. An attacker can use these credentials to access or modify files or data on the FTP server. TCP timestamps and UDP timestamps are vulnerabilities that allow an attacker to estimate the uptime of a system or network by analyzing the timestamp values in TCP or UDP packets. Anonymous FTP Login Reporting is a vulnerability that allows an attacker to access an FTP server anonymously without providing any username or password.