if it's under risk, tplink will update firmware to maintain their product.
I remember there is a FAQ on their official website to state security issue.
You may try to search and confirm that. sorry I can't remember which one.

The answer is probably that you are at risk if all the conditions are right for whoever is scanning you if at all, most router security issues right now relate to risks to those connected to you through wifi rather than your LAN but it's still neither comforting or acceptable imo,

The only things I can offer you for a temp solution until they do update is to ensure you have the most random passwords set, so a good strong 15 unit one for the router and a good random 64 unit one for the wifi password and isolate all your clients so they can't chat to each other if you have that function, it's called AP Isolation if you have it,

Be prepared to wait for a solution as it was a Chinese festival a few days ago and support may need time to catch up if they've been off work during it.

flying snow wrote

I remember there is a FAQ on their official website to state security issue.
You may try to search and confirm that. sorry I can't remember which one.

I found that FAQ and it shows that the C7 V2 and V4 and the C9 V1, V3 and V4 have been fixed but not either version of the C8. :(

Then it gives the following recommendation: " For wireless routers: Make sure your routers are in Router Mode or AP Mode, and patch the operating system of your smartphones, tablets and computers." I have patched Windows and updated my motherboard BIOS. Am I safe in assuming that "router mode" is the default operating mode for a wireless router? I don't see anything in the settings that identifies the mode.

Hannibal Lackluster wrote

The only things I can offer you for a temp solution until they do update is to ...isolate all your clients so they can't chat to each other if you have that function, it's called AP Isolation if you have it,

I see AP Isolation. If I enable that, will it prevent me from casting Pandora from a tablet to my Chromecast Audio?

Yeah it means any client on your network will not be able to communicate with another client on the same network I'm afraid, you may have a setting for rules though that may enable you to place the things that need to see each other outside of the isolation, don't ask I don't know you'll have to have a dig about in the settings, I recommend you use the emulator for your router before trying to find it irl, that way you only need the router admin page open for the minimal amount of time, hth.

I got a reply from Tp-Link customer support saying there would be a firmware update for the C8, V1 but they could not provide a date. They also confirmed that if the router is in "normal router mode" then it would not be affected the the KRACK vulnerability. I guess I will stop thinking about it and just keep an eye open for the firmware update.