semco wrote: I have question , what is the difference between the two.
GroupJive 2.5.1 via GroupJive 2.5 RC2 and
Community Builder 1.8 RC2 via Community Builder 1.8
any one know

Thanks,

RC = Release Candidate

The stable release usually follows.

So GroupJive 2.5.1 is newer than GroupJive 2.5 which is newer than GroupJive 2.5 RC2

==> You need to upgrade to GroupJive 2.5.1 which is the latest at the moment.

Same logic for CB.