Subject: Re: bug#55926: 29.0.50; message.el does not normalize In-Reply-To field from web links

From: Max Nikulin <[email-masked]>
Date: Wed, 15 Jun 2022 23:14:51 +0700

On 14/06/2022 23:27, Robert Pluim wrote:
>>>>>> On Tue, 14 Jun 2022 23:11:45 +0700, Max Nikulin said:
> 
>      Max> Unsure if it is possible to do something really weird through a
>      Max> specially crafted mailto: link (by adding some special headers), but
>      Max> it looks like it is possible to add something that sender may not like
>      Max> to see in its message. So it is better to sanitize input link
>      Max> parameters that are used to generate headers.
> 
> Iʼm not aware of any code in Emacs that calls `eval' or similar on
> parameters passed to `browse-url' or `message-mailto', but you never
> know. Donʼt use Emacs to connect to your bank's website :-)

Actually I did not thought about eval as elisp. I do not like shell 
command in emacsclient-mail.desktop, but this time I wrote about adding 
something suspicious to email messages. However there no way to protect 
against honeypots as Cc aimed to put sender into spammer blocking lists.

> I think Lars' changes here are enough.

I thank Lars for the fix.

There is e.g. References header for the same purpose of proper 
threading, but it may contain list of Message-IDs and there is no 
example of improper format at some site.

I expected something more general e.g. similar to file local variables 
that may be safe or not and sanitizer map for particular headers. It may 
be postponed till next bug report.