Add a flag/option to disallow all network access?

[Michael Weiss <dev.primeos-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

I currently use Pandoc for a somewhat strange(?) use-case: Converting
HTML-only emails to plaintext so that I can read them in Mutt.
I've used a text-based web browser for that in the past but recently
switched to Pandoc because it is better maintained, I trust it more to
securely parse untrusted/arbitrary HTML input [0] (is that correct or
are there any risks?), and most importantly I assumed Pandoc wouldn't
fetch any links, images, style sheets, etc. which would avoid any
tracking and therefore improve privacy.

So far this has worked very well :)
However, when I tested this setup via Email Privacy Tester [1] I noticed
that Pandoc still leaks my IP address (obviously also revealing when I
open/read the mail) by fetching an Iframe [2].

Knowing this I'm wondering if it would make sense to add a flag/option
to disallow any network access (ideally this would even be fairly simple
to implement but I'm not familiar enough with the code / Haskell).
Maybe this is even already possible via the PandocPure [3] monad?
Nonetheless it would be nice to have a CLI option/parameter like
--no-network-access (or even something like --sandboxed or --no-io to
disallow other types of IO as well).

What do you think of this feature request?

Kind regards,
Michael

PS: For my use-case I've noticed that I can avoid this issue by enabling
the raw_html extension (found that in src/Text/Pandoc/Readers/HTML.hs
but it's likely not ideal either although it does at least seem safe for
my use-case(?)). I.e. I use the following now:
text/html; pandoc --from=html+raw_html --to=plain | less
text/html; pandoc --from=html+raw_html --to=plain; copiousoutput

PPS: And thanks for Pandoc btw! It's such an awesome project that I use
for years now.

[0]: https://pandoc.org/MANUAL.html#a-note-on-security
[1]: https://www.emailprivacytester.com/
[2]: https://www.emailprivacytester.com/testDescription?test=iframe
[3]: https://pandoc.org/using-the-pandoc-api.html#the-pandocmonad-class