Change default filename to random

modules/exploits/windows/fileformat/office_excel_slk.rb

@@ -50,7 +50,7 @@ class MetasploitModule  < Msf::Exploit::Remote
       ))
 
       register_options([
-          OptString.new('FILENAME', [true, "Filename to save as", "msf.slk"])
+          OptString.new('FILENAME', [true, "Filename to save as", "#{rand_text_alphanumeric 8}.slk"])
       ])
   end