According to krackattacks.com, An attacker within range of a victim can serious weakness of WPA2 using key reinstallation attacks (KRACKs). Attackers can use this attack technique to read information that was previously assumed to be safely encrypted. This can be abused to steal sensitive information such as credit card numbers, passwords, chat messages, emails, photos, and so on. The attack works against all modern protected Wi-Fi networks. Depending on the network configuration, it is also possible to inject and manipulate data.
If your device supports Wi-Fi, it is most likely affected. Google is expected to fix this vulnerability with its November Security patch, which will be available next month for Nexus and Pixel devices.
MIUI 9 is now available for Xiaomi Redmi Note 4 MTK, Mi 6, Mi Note, Mi Note 2, Mi 5, Mi 5s, Mi 5s Plus, Mi Max, Mi Max Prime, Mi Max 2, Mi 2/2S, Mi 3, Mi 4, Mi 4i, Redmi 2, Redmi 2 Prime, Redmi 3, Redmi 3S, Redmi Note 4G, Redmi Note Prime, Redmi Note 3 Qualcomm, Redmi Note 3 Special Edition, Redmi Note 2, Redmi 4 / 4X, and more devices will get MIUI 9 update soon.