Did they do a stealth update to 15.7.3?

So I was surprised they had an OS update to my iPhone 6S knowing it was locked out of OS updates with the 16.0 land. New one was 15.7.3. Installed it right away. Few days later I noticed it was draining the battery way, way more than it should. I don’t use the phone all that much and typically put it on a charge overnight. Beginning of the day it’s 100% battery, by the time I go to bed it’s 70-80% charged. After 15.7.3 I found it running 20-25% charge after a day’s (non)use where I may only go to the phone for a OTC application a few times. BUT yesterday I noticed a return to normal behavior, 75% charge when I hit the pillow. Got a sneaky feeling it might have been one of the once a decade stealth updates where they tell no one. Anyone got any information that this was in fact, the case?

A larger question is I have seen a number of times where some new OS update caused way more battery use than normal. At this stage of the OS’s lifetime how can this happen? Sloppy Q&A (or less and less Q&A testers ti increase profit by cutting expenses) is about the only reason I can think of… anyone got other ideas?

There are a lot of background tasks being done after many OS updates, which can cause unusual battery drain for a few days afterward. This is usually attributed to major (whole number) updates, but it can happen with incremental updates as well. It depends on what exactly changed in the update. Battery life usually returns to normal without intervention after a few days.

15.7.3 was a security update, which isn’t unusual for a recently superseded OS version. Apple doesn’t typically provide much detail about what’s changed in security updates, but I don’t think it’s unreasonable that a security update might have to do a bunch of background work.

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Not to necro an old thread, but along comes 15.7.6 and my battery life is in the crapper again. Honestly not sure I buy the “2-3 days after an update, battery life will drain hugely because background tasks.” None of this happens on my iPad. Ever. So we shall see…

Oh, start the day at 100% health, do not touch the phone, by 10PM it’s at 14%.