Warning message on boot up after update to Oreo - Sony Xperia XZ

[Android Central Question]

A few days ago my Samsung XZ updated to Oreo, when my battery died I recharged it. Upon rebooting I instantly got a message on the screen which said 'Your device is corrupt, it cannot be trusted and may not work properly', this flashed on the screen for maybe 5 seconds and I did not have time to read the rest of the message, the phone then started normally.

I have turned the phone on and off multiple times since then and the message has not reappeared but I am now hesitant to use the phone. Also, since the Oreo upgrade the phone has been rather slow and the the phone installed AVG Pro Antivirus for Xperia which us Xperia users cannot uninstall. I'm not sure whether the slowing down of the phone has something to do with the AVG program or the message I got on boot up.

Do I have anything to worry about?

 

[Rukbat]

I'd bring it to your carrier and ask them if they can please reflash the update. If the battery died when the update was finishing, it may not have completed. Whether you have anything to worry about is anyone's guess.