Boosteroid will be using Blockchain technology which is close to impossible to hack, so you can rest assure that all malicious thing you're referring to won't go through, unless you're not careful enough. btw if you're file is really that important and you're worried that it might get hacked, i think it's better for you to just save it in your Drive.
This is actually a good point brother, if your main concern is the safety of your most important files, then using your own drive would be the best option, no payment or free, you won't need to worry about the safety and you can access it anytime, even without internet.
And i'm looking forward too for that question, but i think boosteriod is giving your files and anything comfortable so how they not forget about the safety of your files.