lisk Does the beta version have vulnerabilities and can be easily hacked?
I think you'll see that Flarum is very responsive to security issues when they are reported. Beta 7.1 and Beta 7.2 were released within days of being notified of a security issue, just enough time to identify a fix, code it and test it before releasing. Beta 8 should not be vulnerable to hacking, and if you discover any security issues you should email them to security@flarum.org .
lisk I'm not sure what you mean by stable version, for me version 7 stable and 8 unstable version
Our first stable version will be Flarum 0.1.0, without any beta label. The beta period is a time for Flarum to change features and address performance issues before the software is deemed stable. This means both Beta 7 and Beta 8 are inherently unstable versions, and are not recommended for use in production.