Let’s say there is a compromised appvm running in maybe qube: untrusted. It can launch windows apps everything all isolated, but it can trick you. If a window is opened at any time, when typing everything is written to the top window. You don’t have to click it, it automatically types in the first window. Now let’s say qube: untrusted is running also the user is updating a gpg key in qubes:vault. The qubes:untrusted can start notebook or Firefox or even better a special app that can be launched through cli with a very small unoticable window and steal small segments. The user will be able to understand that what they are typing is not going to the qube they want but if an inexperienced user blamed it on a keyboard or slow qubes it may go unnoticed. Especially if the virus is a bit smart and only collects a few words and then closes let’s the user continue and then does it again capturing something secret. This is just an idea but even a word captured could be highly important.
That is a general problem in Qubes.
If I understand your case the malware repeatedly spawns windows and captures
anything typed in to them. What would be captured would be fragments and
the malware would not know in which qube the fragment was originally
intended. So there would be a stream of characters and perhaps words
with no context. Not ideal but not disastrous.
This will only be an issue when the new window would be the active
window. This is a feature controlled in dom0 - KDE controls this, I’m
sure Xfce will also have a setting to prevent it.
I never presume to speak for the Qubes team.
When I comment in the Forum I speak for myself.
This is a low severity “problem” if you would call it that. I just though of it and thought to share it. This could theoretically be exploited.
the issue you describe is called “focus stealing” in the context of window managers. many window manager provide rules to mitigate focus stealing. while it’s mostly an annoyance, it could theoretically be a security issue too - also in Qubes (maybe even more so in Qubes).