Download iOS 11.2.1 (15C153) for iPhone X (Global)

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 iPhone10,3
iOS Version 11.2.1
Release Date 2017-12-13
Update Date 2017-12-10
Sha1sum
16bb3a030157cfde5dce3c5af1682531cac802eb
Sha256sum
d91cfa66eedda82c9284a5e5bd361bbccb624c1285bfdf316cda8dce6f71a724
md5sum
aea307e1421b616bd5c3607240ba5b29
Size 2.76 GB
FileName
iPhone10,6_11.2.1_15C153_Restore.ipsw
Status

Download IPSW (2.76GB) Check device info
Release Notes

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

iOS 11.2.1 fixes bugs including an issue that could disable remote access to shared users of the Home app.

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

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