Xiaomi is rolling out a new MIUI 10.1.1 stable update to users of the Mi 5s. The phone got an update to Android Oreo a while ago and while we hoped that the stable MIUI 10 would be accompanied by Oreo as the base OS, you still get the older Nougat.
The update to Oreo that rolled out to the Mi 5s is still in beta, but a stable version should be outed probably before the end of 2018. As for the stable MIUI 10, the OTA is already rolling out, but you can also grab the firmware from the link below and install it manually.
Note that none of the Oreo and MIUI 10 stable updates are available for the Mi 5s Plus, which leaves us wondering what plans Xiaomi has for the device. Still, it should get both updates sooner or later.
Have no idea how to go about installing the above firmware? Fret not because we have a guide on how to install MIUI 10 on any Xiaomi device, so feel free to consult the linked page.