One security issue I somehow missed back in July was Zenbleed, an issue with AMD CPUs that's getting patched up in the Linux kernel and now the Steam Deck is getting a kernel fix for it too.
Commit 522b1d69219d ("x86/cpu/amd: Add a Zenbleed fix") provided a fix for the Zen2 VZEROUPPER data corruption bug affecting a range of CPU models, but the AMD Custom APU 0405 found on SteamDeck was not listed, although it is clearly affected by the vulnerability.
Add this CPU variant to the Zenbleed erratum list, in order to unconditionally enable the fallback fix until a proper microcode update is available.
So we may see a SteamOS upgrade come in at some point, if Valve chooses to patch it.
I'm sure some people will argue against it as these fixes can come with performance penalties, because the Steam Deck is primarily a gaming device. But still, it has a full desktop mode it's not a traditional locked down console, you can install a browser and do basically anything with it - better to be safe than sorry. The Steam Deck is really just a handheld Linux PC.
More info on Zenbleed here.
If you're on desktop, as always it's a good idea to ensure you regularly check for updates to patch up issues like this. Much like we recently had for Downfall and Inception.