Thanks for bringing this question to the forum. For the past year, I've had a customized Google homepage on Safari. It's all set up the way I want it. Yesterday I downloaded and installed "Fastest Free YouTube Downloader" and today myGoogle homepage has been supplanted by a MyStart homepage. Until today, I was pleasantly ignorent of MyStart's existence.
Interestingly, I shut down my computer twice yesterday, after downloading "Fastest Free YouTube Downloader" and I still had my usual homepage each time I re-opened Safari. That worries me because either MyStart was a little time bomb set to go off later, or they have opened a connection in to my computer, which means I may be in for other surprises in the future.
This doesn't seem ethical. Maybe it's in the fine print somewhere on the "Fastest Free YouTube Downloader" I agree to the following terms and conditions page. If not, then it's illegal. "Fastest Free YouTube Downloader" has been a highly used and recommended program for Macs for several years. Strange that they would be foolish enough to start inserting what looks a lot like malware👿 in to their download.
Thanks to ric_275and applesue7 for solving the mystery!