Use the Msf::Exploit::CmdStager mixin. Fixes rapid7#8092.

Author: pbarry-r7

modules/exploits/windows/ssh/freesshd_authbypass.rb

@@ -10,6 +10,7 @@ class MetasploitModule < Msf::Exploit::Remote
 
   include Msf::Exploit::Remote::Tcp
   include Msf::Exploit::EXE
+  include Msf::Exploit::CmdStager
 
   def initialize(info={})
     super(update_info(info,
@@ -86,7 +87,7 @@ def upload_payload(connection)
     cmdstager = Rex::Exploitation::CmdStagerVBS.new(exe)
     opts = {
       :linemax => 1700,
-      :decoder => File.join(Msf::Config.data_directory, "exploits", "cmdstager", "vbs_b64"),
+      :decoder => default_decoder(:vbs)
     }
 
     cmds = cmdstager.generate(opts)