Alex Dobie, writing for Android Central:
Trump's personal Android phone is more than likely a Samsung Galaxy S3, released in 2012, and which last received a software update in mid-2015, with firmware based on Android 4.3 Jelly Bean.
As noted in the intro, we don't know for sure that Trump is still using this specific Galaxy S3. The two NYT reports conflict on whether he turned it in, or is still using it to fire out tweets from the White House. But if he is, and it's the same consumer GS3 model he was apparently using as of February 2016, it's safe to say it's a good three years out of step with the latest Android security updates. Many Android security scares have come and gone since the GS3 got its last update in August of 2015.