Windows 10 Accounts Port per Gary Guo

Starting in Firefox 91, Firefox has direct integration with Windows SSO so this extension is no longer needed. Please check out https://support.mozilla.org/en-US/kb/windows-sso for how to enable it.

Sign in to supported websites with accounts on Windows 10. Ported from the Chrome's Windows 10 Accounts extension.

Windows 10 have a native messaging host for Chrome preinstalled. To make it work for the Firefox port, the following steps should be taken:

Create a file C:\Program Files\Windows Security\BrowserCore\manifest-firefox.json with contents
{
"name": "com.microsoft.browsercore",
"description": "BrowserCore",
"path": "BrowserCore.exe",
"type": "stdio",
"allowed_extensions": [
"{d4a5b766-4831-43f0-9d38-0fec359491e7}"
]
}

Then execute
REG ADD "HKCU\Software\Mozilla\NativeMessagingHosts\com.microsoft.browsercore" /ve /t REG_SZ /d "C:\Program Files\Windows Security\BrowserCore\manifest-firefox.json" /f

to add it as a native messaging host. You can also replace HKCU with HKLM to add for all users.