If you are using FileMaker 16, you probably got a notice that an update to version 16.0.4 was released this week. It's a solid update and you ought to install it.
This only applies to users running FileMaker Pro on their computers. If you're access ing Rucksack apps in your web browser, you do not need to worry about this.
William Porter is Rucksack's owner and principal. He's been writing on a range of tech subjects for three decades. Yikes!