Keycloak 18 openid logout - 404 (due the 2800 characters limit in the HTTP query for the IIS server)

Describe the bug

Hi.

We've recently updated our keycloak to 18.0.0. Everything worked fine, automatically, except the logout mechanism. Our site was still using redirect_uri. We updated the frontend to use the most recent keycloak-js. Now it is sending post_logout_redirect_uri and id_token_hint correctly.

And here is the issue, the logout is resulted in a Server Error: 404 " 404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable. "

I read that the 18 keycloak now asks confirmation to logout. We are using a custom template for the client. Do we miss the page for the logout confirmation from our template? If so, where can I find a sample template for this?

Would be nice: to display the error message in the log, what is not found exactly.

Cheers, Ádám

Version

18.0.0

Expected behavior

User logs out

Actual behavior

404

How to Reproduce?

Probably: Use a custom template from an older version.

Anything else?

No response