The last security-centric AirPort update prior to Thursday's 7.8.1 for this model was version 7.7.9 in December 2017. Version 7.8 was only for the AirPort express, and added AirPlay 2 features in
Apple Releases AirPort Base Station Firmware Update 7.8.1 Jun 20, 2019 About AirPort Base Station Firmware Update 7.9.1 May 30, 2019 Apple Airport Utility for Windows - Free downloads and apple airport utility free download - AirPort Utility, Apple AirPort for Windows, iPhone Configuration Utility for Windows, and many more programs This software is available to download from Apple Releases AirPort Base Station Firmware Update 7.9.1
Oct 16, 2017
Apple updates AirPort Base Station software for Mac and PC
Apple Releases AirPort Utility 5.5.3 for Mac and Windows
Update the firmware on your AirPort base station - Apple Jun 21, 2019