Detailed description what you could do with a malicious npm package is currently on he front page: "Harvesting credit card numbers and passwords from websites"
Hey, I wrote that article :) - yes it was pure coincidence, I just decided with all the security stuff going on this week (Spectre/Meltdown, I hadn't heard about the npm stuff) I'd write and article about it.
https://news.ycombinator.com/item?id=16084575