Juli Clover, writing for MacRumors:

Apple now has a dedicated iCloud Passwords add-on designed for the Firefox browser, which means Firefox users can access passwords and logins stored in the Passwords app or iCloud Keychain when using Firefox on a Mac. 

The extension requires macOS Sonoma or later and isn’t available for Firefox on Windows or other operating systems. But it’s a start, at least.

➝ Source: macrumors.com