Download iOS 12.1.3 (16D39) for iPhone 6s+

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

❌ This IPSW firmware is not being Signed by Apple

Firmware Identifier iPhone8,2
iOS Version 12.1.3
Release Date 2019-01-22
Update Date 2019-01-11
Sha1sum
9ff3ff7360f23b2ce0bed6b3354c0dab4415c35e
Sha256sum
8cf0756c66342c16526d35acc69c98fa2114cd6c6cdb4bf2114c8bbd501b4c13
md5sum
90f008ba0d4cea85e9a9713e1fad660e
Size 3.05 GB
FileName
iPhone_5.5_12.1.3_16D39_Restore.ipsw
Status

Download IPSW (3.05GB) Check device info
Release Notes

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

iOS 12.1.3 includes bug fixes for your iPhone or iPad. This update:

This release also includes bug fixes for HomePod. This update:

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

https://support.apple.com/kb/HT201222