Quoting airmoose (airmoose@???):

> Since there is currently some discussion about Chrome/Chromium
> security concerns, is Vivaldi (based on Chromium code I understand)
> also affected with the same security issues?

It's proprietary. Thus, it's the sponsoring company's black box where
security matters are concerned, and (on a different subject) at risk of
being EOLed without anyone else having the legal right to take over
maintenence).

Maybe Vivaldi Technology AS is the world's most benevolent company.
They're Norwegian, so they can't be all bad.[1] But with proprietary
code, you are in a position of inherent need to trust some firm. In the
subcase where it's not merely proprietary but also binary-only,
outsiders can do only limited checking. (Vivaldi browser is binary-only.)

My personal FAQ pages include an item that lists all known Web browsers
for Linux, with ultra-brief characterisation of each. These are not
reviews, but might be useful as a point of departure if, say, you wish
to compare open-source Web browsers on Linux and wished to not spend
time on proprietary ones.

http://linuxmafia.com/~rick/faq/kicking.html#linuxbrowser

> If no one knows, what procedure do I go through to determine the
> answer myself....

Best way: Be a member of a community of committed open source people
who manage, very imperfectly but intermittently, to look after such
matters. If you _personally_ wished to study security concerns
involving Web browsers, there are several approaches that can bear some
fruit, including studying source code (obviously not a go for
binary-only proprietary software), using tools to monitor its
interaction with networks (e.g., wireshark) and the host system, and
intensively study its user-facing controls.

And remember the truism that, if you aren't the customer, you're
probably the product, i.e., if a company produces a Web browser you can
use, it's always timely to consider where the firm's revenue stream
comes from. It might very well involve quiet compromise of your privacy
and security.

> ...(with the understanding that I am basically a computer
> idiot, but I quit Windows entirely in 2004 and became an Ubuntu user
> until earlier this year when I jumped on to Devuan).

Welcome!


[1] But my Tante Bjorg warned me not to trust them, so you're on your own.