Chinese seller, Refurbished HTC one and security issues.

[finblockchain1]

I bought a refurbished HTC one from Ali Express. I can not use netbank on that mobile as netbank shows security warning and netbank app does not work on that phone. But I use that phone to send and withdraw coins from wallets. Is there any possibility to be hidden app or malware that can send my wallet key to someone(hacker)? Is it risky to use that phone for wallets.