Download iOS 13.3.1 (17D50) for iPhone 6s

You will have to note that you can only restore signed IPSW firmware files using iTunes or 3utools.

Firmware Identifier	iPhone8,1
iOS Version	13.3.1
Release Date	2020-01-28
Update Date	2024-06-03
Sha1sum	90941bd17d68ba09d3719ca96f75c6038ff65c08
Sha256sum	e31085f1601e0dd9d0dfea6a021407de70f94b904fabaa9f2137a276c63e159c
md5sum	d955380242e4851f35ee6b2197fa1e07
Size	3.46 GB
FileName	iPhone_4.7_13.3.1_17D50_Restore.ipsw
Status

It should be noted that these are the official release notes for the from Apple

iOS 13.3.1 includes bug fixes and improvements. This update:

Fixes an issue in Communication Limits that could allow a contact to be added without entering the Screen Time passcode
Adds a setting to control the use of location services by the U1 Ultra Wideband chip
Addresses an issue that could cause a momentary delay before editing a Deep Fusion photo taken on iPhone 11 or iPhone 11 Pro
Resolves an issue with Mail that could cause remote images to load even when the “Load Remote Images” setting is disabled
Fixes an issue that could cause multiple undo dialogs to appear in Mail
Addresses an issue where FaceTime could use the rear facing ultra-wide camera instead of the wide camera
Resolves an issue where push notifications could fail to be delivered over Wi-Fi
Addresses a CarPlay issue that could cause distorted sound when making phone calls in certain vehicles
Introduces support for Indian English Siri voices for HomePod

For information on the security content of Apple software updates, please visit this website: