The Weekly update 8.1.18 has been officially released for Mi 5s Plus (codename is natrium). Before updating, please make sure you have downloaded the exact ROM matching your Xiaomi phone/tablet. In Fastboot mode, you can check model code by typing fastboot getvar product in cmd/shell.
The firmware files posted here are all official Xiaomi MIUI or HyperOS ROM, xiaomiROM.com do not own and never modified those firmwares，you will always download the file from Xiaomi server.
You may interest in those contents: Mi 5s Plus ROM Topics Xiaomi Devices Index
Download Mi 5s plus (natrium) China MIUI 8.1.18 Recovery ROM with Android 7.0. Firmware size is 1.6 GB.
Download Mi 5s plus (natrium) Global MIUI 8.1.18 Recovery ROM with Android 7.0. Firmware size is 1.5 GB.
Download Mi 5s plus (natrium) Global MIUI 8.1.18 Fastboot ROM with Android 7.0. Firmware size is 1.7 GB.