Qt 5.9.8 is released today. As a patch release Qt 5.9.8 does not add any new functionality, but provides security fixes and other improvements.
Compared to Qt 5.9.7, the new Qt 5.9.8 contains multiple security fixes, updates to some of the 3rd party modules and close to 20 bug fixes. In total there are around 130 changes in Qt 5.9.8 compared to Qt 5.9.7. For details of the most important changes, please check the Change files of Qt 5.9.8.