Apple last month issued an to the firmware for all AirPort devices to fix a serious flaw. 
Impact: A remote attacker may be able to cause arbitrary code execution Description: A memory corruption issue existed in DNS data parsing. This issue was addressed through improved bounds checking.
Airport Utility For Mac 6.3.4
Airport Utility Download Page
The latest version of AirPort Utility (6.3.8) is an included part of the High Sierra operating system, so it is of course fully compatible with High Sierra. Or, stated another way, if you have High Sierra installed on your Mac, you also have the latest version of AirPort Utility (6.3.8) installed on your Mac. 
In order to provide the best platform for continued innovation, Jive no longer supports Internet Explorer 7. 
Attention, Internet Explorer User Announcement: Jive has discontinued support for Internet Explorer 7 and below.
Airport Utility For Mac Sierra
But if you don’t have AirPort Utility set to automatically check for updates, you wouldn’t know about it unless you happened to open the app. You can do this by opening Airport Utility and then Preferences. Ensure that all the boxes are checked, and that the check is set to Daily for maximum protection or Weekly otherwise. That way, you’ll be automatically alerted if an update is available.