Trojan horse possible with news readers

[Joseph S. D. Yao]

In article <6775 at rosevax.Rosemount.COM> merlyn at ernie.rosemount.com writes:
>			   ... some versions of vi will execute
>commands if it sees a line (near the top or bottom of a file)
>of the form <e><x><:><command><:>

System V Release 3 has a "modelines" attribute, which defaults to
"nomodelines".  This is a Very Good Idea (defaulting to off).

I have added other necessary fixes.  The check is, roughly, to find
the first ':' and then check for the previous two characters' match
with "ex" or "vi".  The necessary fixes are:
	(1) Check that the ':' is not one of the first two
	    characters, otherwise you will be checking against
	    non-existent characters on that line.
	(2) Check that either the ':' is exactly the third
	    character on the line, or that the third character
	    back isspace().  Otherwise, lines like:
levi:PASSWORD DELETED:Dolly Levi of Upstate NY:/usr/levi:/match
	    will trigger the "feature".

	Joe Yao			uunet!hadron!jsdy