Sudden problems with 2FA USB keys on Kubuntu

[whoami]

Hello, All

I know this is a long shot, but suddenly (as of mid-April 2024) I started having problems with my Yubikeys just blinking once after insertion and then not being recognized by the browser.
I tested this on 3 different machines running Kubuntu 22.04 LTS.
Computer #1 that hasn't been updated in over 3 months: keys work without problems on Firefox (they keep blinking until I touch to confirm).
Computer #2, fully updated, keys stopped working in Firefox but work in Chromium. I updated Firefox (snap) and the keys worked but suddenly stopped after one session (??)
Computer #3, fully updated, keys stopped working in Firefox, don't work in Chromium (same exact version as on Computer #2) but I installed Brave and the keys worked.
I used lsusb and the key is properly identified by the system. It's definitely NOT a bad key (or two that both suddenly got bad).

This is insane.
Can anyone confirm this behavior? I've had these keys for a few years and there was never a problem before.

[Schwarzer Kater]

This certainly sounds insane…

Although it is quite unlikely: did you try new user accounts on all machines - and different USB ports…?

Another test could be to install the "traditional" Firefox additionally to the Snap and try if this behaves differently (it is easily removed again if this changes nothing - just use the script…):
install traditional Firefox script

[whoami]

This certainly sounds insane…

Although it is quite unlikely: did you try new user accounts on all machines - and different USB ports…?

Great suggestion! I created a new user on my up-to-date machine. The key worked in Firefox as expected.
"User settings" I thought - something in my config causes Yubikey problems that were not there before.
Upon logging in back to my account, I encountered a problem with Plasma not letting me back in (black screen).
Hard reboot, and... my keys started working on my account, in the same Firefox.
As much as this appears to work now, I expect more trouble down the road. Reboots on the other machine did not fix the problem, still looks like some wrong planets had aligned on two separate computers

[whoami]

OK, this weird problem has something to do with Firefox storage - it definitely looks like a bug (I'm on version 124).
After reboot, when Firefox is in "fresh" state (whatever that means), the authentication works as normal.
After using "clean recent history" (I strongly suspect website data flush is the culprit) the authentication keys stop working, even after restart.
It just so happens that one of my computers cleans history on Firefox close, so this error is being triggered perpetually. In other words, on this particular computer, it's enough I start Firefox once, close it, and it won't work again until just once, after reboot.

Closing and re-restarting Firefox session again somehow restores the order, and keys work as intended (a dialog box pops up asking user if he/she wants to share key data with the site).

[Schwarzer Kater]

Perhaps it may be worth to look into about:config and then for example browser.sessionstore.resuming_after_os_restart or browser.sessionstore.restore_on_demand or similar settings in Firefox (or in the Firefoxes )…

I have to point out the possibility to install an additional "traditional" Firefox again.
Then you will also have completely separate settings from the Snap.