I wrote about that here: https://news.ycombinator.com/item?id=35925239
In my experience their attention is strongest towards the end of the last message, which could be the reason for injections being so effective with little effort. Within the OpenAI models as of today the first user message is much stronger than the system message.
Given the ChatML spec and their end-to-end control over the models, I wonder whether the system message could end up being sandboxed by architecture and/or training.