I don't think this is a part of browser interface. You can block third-party cookies for accounts.google.com to remove your account from this popup. Or use an ad blocking extension to hide this prompt and block third-party requests.

It even shows up when I delete the entire html document:

It is a native browser popup

Found the culprit and honestly surprised this isnt off by default or even removed entirely.

@networkException @Ahrotahn Is it worth flipping this setting by default?

With our changes the identity provider should return that the profile is not signed in. Granted, we should probably add that section to the UI removal patch since it doesn't, or at least shouldn't, do anything.

I tested with my local linux build as well as the windows builds for 122.0.6261.94-1 and 124.0.6367.207-1 from our binaries page and I'm not able to reproduce this.

Are you using a third-party build? Maybe they are not building with our sign-in changes.
Are you using a profile that was used with another browser? Maybe there is a variable that got set in the profile that we didn't expect to be changed.

I tested https://github.com/ungoogled-software/ungoogled-chromium-windows/releases/tag/124.0.6367.207-1.1 - ungoogled-chromium_124.0.6367.207-1.1_windows_x64.zip (@teeminus) (only default settings, no extensions installed, absolutely clean)

and indeed it turns out that the default setting is not what it should be:

I confirm @Swarkin's point.

@Rusenche The interface option for the setting existing wasn't in question. Can you reproduce the Google sign-in dialog this issue is about?

@Ahrotahn

Are you using a third-party build? Maybe they are not building with our sign-in changes.

I am using the windows build from the builds website linked in the readme on version 122 as that is the last version without the UI refresh.

Are you using a profile that was used with another browser?

I only imported a bookmark html file and the browser was one of the first things I installed on a fresh windows ltsc install, so no other browsers were present.

I'll see what I can figure out. It might be better to remove fedcm functionality alltogether.