A UX designer might have told them it was a bad idea to deploy the patch widely without testing a smaller cohort, for instance. That’s an obvious measure that they skipped this time.
I bet my ass UX is not anywhere close to the low-level OS team.
UX is definitely embedded in the App level team but not in low-level.
Granted, a company that isn’t focused on the user experience as much as it is on other things might not prioritise this as much in the first place.
Software security and quality is the responsibility of everyone on the team. A good UX designer should be thinking of ways a user can escape the typical flow or operate in unintended ways and express that to testers. And in decisions where management is forcing untested patches everyone should chime in.