The Matt Wright guestbook.pl <= v2.3.1 CGI script contains a flaw that may allow arbitrary command execution. The vulnerability requires that HTML posting is enabled in the guestbook.pl script, and that the web server must have the Server-Side Include (SSI) script handler enabled for the '.html' file type. By combining the script weakness with non-default server configuration, it is possible to exploit this vulnerability successfully.
To display the available options, load the module within the Metasploit console and run the commands 'show options' or 'show advanced':
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