Npgsql 3.2.7 contains some important fixes, and includes support for some PostgreSQL 10 features, notably SCRAM-SHA1-256. It's recommended that everyone upgrade.
The list of changes is available here.
Npgsql 3.2.3 contains some important fixes, everyone is encouraged to upgrade. This version notably introduces support for .NET Standard 2.0, which is still in preview but can be used.
The full list of changes is available here.