PayPal is still running on something they call XPT and their admin tools are built with something called Maxcode (Max Levchin wrote it).

As of 2 years ago they revolutionized CSS by having it being generated from Java because their fellowship of the ring wanted control over which properties you can use and how. Everything they do from a tech perspective has been to allow them to hire cheap labor while restricting which HTML/CSS they have access to. It's probably a good business strategy (like making sure they don't get classified as a bank) but it fosters an abysmal tech culture.

I have no way to prove the points above you'd just have to trust that I worked there as a UI dev.