[Mimedefang] HTML Mail / Active content filter

Dianne Skoll dianne at skoll.ca
Tue Apr 11 10:38:36 EDT 2023

On Tue, 11 Apr 2023 16:23:53 +0200
Florian Lohoff <f at zz.de> wrote:

> Javascript in emails is sub 0.1% - Its basically not in use.

I just checked my inbox.  Email notifications from Airbnb use
Javascript. So you will definitely block valid (for some interpretation
of "valid") email if you block all email with Javascript.

However, if you want to do it, then blocking any HTML part with a
<script> tag in it should be all you need.  This can easily be done with

> And after 3 Weeks of Downtime the mood is currently to even block
> all Microsoft Formats (docx, pptx, xlsx and the like) which
> we do right now.

That would *definitely* be a problem for me, but if it works for your
organization, then go for it!

> So my biggest concern is Mail with Javascript (Which was the origin)
> and PDF with active content.

Detecting active content in PDF is much trickier than detecting it in
HTML.  I assume you could use PDF::API2 and rummage through the
objects in the PDF file, but I don't know how PDF::API2 returns
active content.  You'd need to experiment.


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