A quick glimpse at his official Twitter account also makes it clear that his most explosive tweets are still coming from "Twitter for Android," which has been generally been a sign that he's writing them himself. Meanwhile over at the official @POTUS account, we're seeing less hyperbolic tweets from Twitter for iPhone, which is a big hint that they're coming from an aide. It was hard to imagine that Trump would give up on his Twitter addiction entirely, but it's still surprising to see that he's still relying on his same combative tone, even though he's officially President.
Given how much attention Trump paid to Hillary Clinton's private email server, you'd think he'd be careful about opening himself up to similar scrutiny. Of course, tweeting from a personal account is different from storing potentially confidential emails, but Trump's Android phone is still a dangerous vulnerability. We don't know if he's actually dealing with government information on the device, for one, and it's a pretty obvious data goldmine for hackers and thieves. And even if Trump enabled biometric authentication and device encryption, his old Android phone still wouldn't be up to the security levels required for his position.
Update: As AndroidCentral points out, it also looks like Trump isn't just using an unsecured Android phone, he's using a 2013-era Galaxy S3. That's particularly disturbing since the S3 hasn't received a security update since the middle of 2015, and it's most likely running a practically ancient OS, Android 4.3 Jelly Bean. If true, it means the President of the United States relies on an incredibly vulnerable device day-to-day just for tweets.