Ubuntu does not change package versions within a release
A new version of Ubuntu is released every 6 months and every fourth release is an LTS (Long Term Support) release, which means new LTS releases come out every 2 years.
Once an Ubuntu release has been completed and published, updates for it are only released under certain circumstances, and must follow a special procedure called a “stable release update” or SRU.
This means that in practice, within a given Ubuntu release, package versions are stable. There might be patch-level updates to packages to fix bugs, but as a rule, Ubuntu does not upgrade to newer versions of software.
When security issues are found in open source projects, a fix for this is often released as a new version (because most projects don’t have the resources to backport fixes to older versions). To make this work with Ubuntu’s release cycle, those security fixes are typically backported to the version of the software that is contained within a given release by Ubuntu’s maintainers.
The result of this release cycle is that, as a user, there is a high degree of certainty that upgrading packages will not introduce any new features or change existing behavior.
Only when you decide to upgrade the Ubuntu release you are running (for example, upgrading from 18.04 to 20.04) will you get new software versions for which you will need to pay a much closer attention to any upgrade notices.