I did not install any plugins or add-ons. It is also
strange that the file was last modified on Oct 17,
because on a different installation I found version
1.7.1 with an *earlier* modification time (but here
third-party plugins were installed and removed several
times with no possibility of reconstructing what
It is quite difficult to find out exactly where this
binary comes form and whether it is the "official" one.
The binary files by Cisco that can be regularly found
on the web are different.
A user in the Debian IRC channel told me that he found
a reference to http://ciscobinary.openh264.org/ openh264-linux64-0410d336bb748149a4f560eb6108090f078254b1.zip
in /usr/lib/firefox-esr/omni.ja which I also have.
And indeed this is the binary that I found on my system,
so it seems to be something official.
Nevertheless, I think this is not the expected behaviour.
Unfortunately, starting firefox from an empty profile does
not automatically download the file. Something else
must have triggered the download, which I could not reproduce.
(Just speculating: Maybe visiting certain websites or starting
firefox after being updated by "apt upgrade", which happended