Apache 2.4 on Windows 2008 large file downloads are corrupt

When you access /monitorix in a browser, you are accessing /var/lib/monitorix/www. Your Directory block allows access to /var/lib/monitorix/www/cgi, not /var/lib/monitorix/www. Either change the Alias to:

Alias /monitorix /var/lib/monitorix/www/cgi

or add an additional Directory block:

<Directory /var/lib/monitorix/www/>
    <IfModule mod_authz_core.c>
            # Apache 2.4
            Require all granted
    </IfModule>
    <IfModule !mod_authz_core.c>
            # Apache 2.2
            Order deny,allow
            Allow from all
    </IfModule>
</Directory>

As for seeing the source of the cgi, it's probably mod_cgi's configuration. Either it's not enabled or it's not set to handle *.cgi files. You may need to add:

AddHandler cgi-script .cgi

to your virtualhost or directory block. If that doesn't work, try this in your shell:

sudo a2enmod cgi

and follow the instructions to reload apache. If it still doesn't work, add a comment below and possibly update your question. I'll take another look and maybe set up a test system.

It looks like you have forgotten DirectoryIndex.

This should be added to the <VirtualHost> serving WordPress.

DirectoryIndex index.php