Is FileCloud safe?

Yes

Safe from what? If looking at hacker proof, I'd never say anything was hacker proof, but in the many years we have been using it, there has been new large exploits, and the dev team releases constant updates as they find any issue, no matter how minor. Since you can run it either local or cloud based, I would say it is as safe as the security you setup for your users. Let them use easy passwords and no MFA, then no, it will not be very safe. Use all best practices and it will be as safe as humanly possible at this time.