> They have a full power JavaScript runtime engine running as SYSTEM. No sandboxing, no lowprivs, and the whole point is to run untrusted code.

I would have understood that if it was a small company and a lone developer made a mistake. However, this is Microsoft, a huge company. Lone developers don't get to decide things like this at companies the size of Microsoft. Most likely, meetings were held, architects were involved, code was reviewed. How did such a horrible decision make it through that process ?