It works perfectly on the latest Mac OS & Firefox versions.
Not sure why people complain it doesn't on Windows. The description of this extension states it clearly:
"The iCloud Passwords extension is compatible with macOS Sonoma or later. It is not available for Windows at this time."

Didn't you read that?

I was waiting for this for ages. Thank you Apple.

Works perfectly on Firefox (including 133). Just make sure you have an active session (click extensions icon then select iCloud passwords).

Super! No problems. On iMac M1 and MacBook Pro M4 14" both with Sequoia 15.1.1 and Firefox 133.0

Works like a charm. finally! (FF 133.0, macOS)

Works like a charm. (MacOs Sequoia + Zen Browser)

STUNNING - so grateful to Aurélien for putting in the effort to bring apple passwords to firefox! Works really well on Sequoia too, especially once I figured out how to turn on In-Page Auto-Fill

Works well on Sequoia

Works as expected on macOS 15.1. Hoping 2FA autofill can be brought to extension at some point.