You can use
nc) to communicate with another machine (e.g. host), if it also has netcat installed. Netcat is pre-installed in Tails, and most Linux disributions, and available for Windows as part of Cygwin or MSys, or standalone.
First start the
netcat in listen mode (on the non-Tails machine, e.g. VirtualBox host):
nc -l 7777 > some_file.zip
Then send the file from Tails:
nc 10.0.2.2 7777 < some_file.zip
Host OS in VirtualBox, when NAT is configured, usually has IP
10.0.2.2 so the commands should work as is. Don't forget to change
One caveat: there will be no transfer progress displayed and when it's done, nothing will happen. So you might check the file after some time, to determine if it has completely copied or not.