Download iOS 13.1.3 (17A878) 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 iPhone8,1
iOS Version 13.1.3
Release Date 2019-10-15
Update Date 2019-10-10
Sha1sum
96be7a8e55ec4bd1867bd1d7f18b1f24f8731838
Sha256sum
d50f787620a9df5ba65d4880287ad6eb95abf76b77ce235fc1893efbefc52b40
md5sum
e7f95f23dd0d8f406b2ef95d4b63bc5c
Size 3.40 GB
FileName
iPhone_4.7_13.1.3_17A878_Restore.ipsw
Status

Download IPSW (3.40GB) Check device info
Release Notes

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

iOS 13.1.3 includes bug fixes and improvements for your iPhone. This update:

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

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