A year or so ago, my Synology NAS got hacked by a Bitcoin mining virus. I only discovered it because a tech blogger tweeted about it and I happened to see it. My Synology was out of date and the virus must have exploited a vulnerability without any action on my part. Without knowing what to look for, the virus was effectively invisible. Given that I'm probably in the top 1% of tech savvy people, imagine how many others must have gotten infected! (I contacted Synology tech support and suggested that they send out an e-mail to their users, but they never responded.)

Unfortunately, last I checked, it's still impossible to have a Synology NAS automatically update itself.