Apple has released updates for iOS/iPadOS, macOS, and watchOS that mostly fix bugs and security vulnerabilities.
iOS 15.3.1 is a minor update for most users in terms of features. Fixes an issue with braille displays and fixes an arbitrary code execution vulnerability.
Apple's iOS update notes are as follows
iOS 15.3.1 provides important security updates for your iPhone and fixes an issue that could cause braille displays to become unresponsive.
Additionally, Apple has posted information about security updates on its support website:
Available for: iPhone 6s and later, iPad Pro (all models), iPad Air 2 and later, iPad 5th generation and later, iPad mini 4 and later, and iPod touch (7th generation)
Impact: Processing of maliciously crafted web content may lead to arbitrary code execution Apple is aware of a report that this issue may have been actively exploited.
Description: A use after free issue was addressed with improved memory management.
CVE-2022-22620: an anonymous researcher
Meanwhile, macOS Monterey 12.2.1 primarily fixes a bug that can cause Macs to unexpectedly drain their battery. Here are the update notes:
macOS 12.2.1 provides important security updates and fixes an issue for Intel-based Mac computers that could cause the battery to drain during sleep mode when connected to Bluetooth peripherals.
The bug garnered press attention a few weeks ago when users claimed their MacBook batteries died or near zero even when the laptops were asleep and not in use.
The behavior occurred because Bluetooth accessories were repeatedly waking up the Macs they synced with, but Apple says it fixed the issue with this update. macOS 12.2.1 also fixes the same WebKit issue as iOS 15.3.1.
Apple also released watchOS 8.4.2 for Apple Watch today, but simply says the update fixes bugs and provides security updates, without elaborating.