For version 8.9 it is necessary to reinstall the software to benefit from the updates.
Prior to version 8.9, the build consists of a single file : “hgui.zip” (or hgui.jar depending on your browser / browser configuration).
For the update to be installed, the file should be copied into the following directory: <hugin installation directory>lib
And renamed to hgui.jar. This will replace the existing hgui.jar file.
This is all it takes to install the update.
It is not necessary to install all the updates. The latest update always contains all prior updates as well.
Note, that updates are only available for the latest releases.