While the official app from Microsoft was safe and free of malware, downloading the app file from unofficial file-hosting sites poses a security risk. Since the app no longer functions as intended due to server shutdowns, there is virtually no benefit to installing it from third-party sources today.
Disclaimer: This post is for archival and informational purposes. Microsoft no longer supports Windows 10 Mobile, and updating may expose your device to security risks. windows 10 mobile upgrade advisor app download free