What is the current software revision for the Apple Time Capsule?
I have observed a few potential security vulnerabilities with release 7.9.1, is there something more current?
7.9.1 is the most recent update. Since it has been more than 18 months since the last update, and the AirPorts were discontinued in April 2018, I would not expect Apple to provide any future updates for the Time Capsule and other Apple routers.