The current stable version of Dunst is 1.4.0 released on Mar 30 2019.
There has been significant internal refactoring since the last release which might have introduced some new bugs. Be sure to report anything you find. However, as usual, there has been a lot of bug-fixing and a lot of new features have been added as well. Look at the full changelog for a breakdown. Some important points to note:
In the previous release we introduced support for clients to mark notifications as ‘transient’. Transient notifications used to 1) bypass idle_threshold and 2) not be saved in history. The latter behaviour has been disabled by default and can be re-created using rules if necessary. Transient notifications will now only bypass idle_threshold.
Additionally, to be compliant with the notification spec, the notification summary no longer accepts markup.