The most effective next action is to investigate /cgi-bin/debug.sh because it is a direct, high-signal finding: a server-side script in a CGI-enabled directory that is reachable without authentication. In PenTest+ enumeration methodology, testers prioritize items that are both accessible and likely to yield immediate impact, such as unauthenticated administrative/debug endpoints, exposed scripts, and functionality that could enable command execution or information disclosure. A debug shell script exposed through cgi-bin is a classic candidate for sensitive data leakage (paths, environment variables, credentials) or unsafe parameter handling that can lead to remote command execution—especially when mod_cgi is enabled and the file is callable over HTTP.

By comparison, uploading an msfvenom payload assumes a write primitive to /admin and an execution path, neither of which is established by the findings. Nikto can be useful, but it is redundant compared to the specific, actionable lead already identified. Brute-forcing SSH is noisy, may violate rules of engagement, and is less efficient than testing an unauthenticated web-exposed script first.