where is change log? do I have to upgrade?

Where can I find changlog of your extensions?

current versions:
- com_communitypolls_v2.0.15 + com_cjlib_v1.1.8
- mod_randompoll 2.0.9

Do we have to upgrade to:
Community Polls v2.0.16
CJLib v1.1.9
mod_randompoll v2.0.10
?

I don't know if new versions are because of some vulnerabilities or some minor things.