Add Caution

README.md

@@ -4,3 +4,15 @@ https://feitiantech.github.io/OpenSK_USB/
 Googel released [OpenSK](https://github.com/google/opensk), which is  is an open-source implementation for security keys written in Rust that supports both FIDO U2F and FIDO2 standards.
 
 This site opens all the materials in Feitian OpenSK USB Dongle, include hardware and casing design.
+
+
+### Caution
+
+!!! warning ""
+    You should read the following notes before you try or buy our OpenSK dongle.
+
+1. Please keep in mind that OpenSK is a research platform, Google hopes it is used by researchers, security key manufacturers, and enthusiasts to help develop innovative features and accelerate security key adoption. Feitian OpenSK dongle is manufactured for researchers or enthusiasts to learn what FIDO is and how it works. It is not intended to be used for the circumstance that needs highest security.  
+
+2. The core nRF52840 chip is just a **microcontroller** instead of a **secure element**, so this OpenSK dongle may not resist some advanced hardware and physical attacks. It is not much safe to protect your personal online account and secret data as other Feitian FIDO security keys can do. So if you are a government officer, journalist, activist, or someone else at risk of targeted online attacks and need deeply secure protection, we recommend you to use our commercial [Feitian FIDO security keys](https://www.ftsafe.com/Products/FIDO).  
+
+3. Except for some advanced hardware and physical attacks, OpenSK is still a better choice to protect your online account remotely. If you want to use it to protect your personal data, please keep it safe and do not provide it to any other one wittingly or involuntarily.  

docs/index.md

@@ -16,6 +16,9 @@ To help and accelerate FIDO security key adoption, FEITIAN improves the housing
 
 Before you try to program firmware to OpenSK, please read the original [OpenSK guide](https://github.com/google/OpenSK) at first. The following documents are most like additional remarks.
 
+!!! warning "attention"
+    Before you try or buy Feitian OpenSK Dongle, please be sure that you have read the important [caution](./caution.md) message.
+
 ### OpenSK Model
 We have two models of OpenSK USB Dongle, V1 and V2. They are designed according to the [nRF52840 USB dongle](https://www.nordicsemi.com/Software-and-tools/Development-Kits/nRF52840-Dongle), which is used by Google OpenSK firmware. The difference between V1 and V2 is the method to enter bootloader mode.  
 

mkdocs.yml

@@ -49,4 +49,5 @@ nav:
   - Test FIDO: 'test.md'
   - Hardware: 'hardware.md'
   - About: 'about.md'
+  - Caution: 'caution.md'
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