Recently, every time I've tried to use Microsoft authentication with a provided email and password, it's always given me the exception Invalid password or access token.

It was working before and I didn't change anything about my code, so I think Microsoft probably changed something internally.

Nothing has changed about the account I was using either, and I can still log into it normally on a regular Minecraft client.

As an additional note, when I was debugging, I found that this type of authentication still seems to work when I use a different library called node-minecraft-protocol. As far as I can tell, that library seems to authenticate the same way that this library does (node-minecraft-protocol's XboxTokenManager uses https://github.com/XboxReplay/xboxlive-auth), so I don't know why it's not working here.