bug#28350: enriched.el code execution

[Eli Zaretskii]

> Date: Sat, 09 Sep 2017 22:37:29 +0200
> From: charles@aurox.ch (Charles A. Roelli)
> CC: 28350@debbugs.gnu.org
> 
> Thank you.  I've kept the current approach.  Please see again the
> attached patch.

Some minor nits below.

> Also, should the left-fringe/right-fringe display specifications be
> considered safe?  They seem innocuous.

Yes, I think so.  And your patch already does allow them, doesn't it?

> +(defcustom enriched-allow-unsafe-display-props nil
> +  "Variable determining whether to decode arbitrary display properties.

"If non-nil allow to evaluate arbitrary forms in display properties."

> +  :risky t
> +  :type 'boolean
> +  :group 'enriched)

Please add :version here.  Please also add a short NEWS entry.

It would be good to have tests for this, but doing that is much less
urgent than fixing the vulnerability, so please feel free to do so as
a separate commit (unless you already have the tests ready).

Otherwise, looks good to me.  Thanks.