Security Trimming with Microsoft 365 Copilot: Asking the Right Data in the Right Context

The more I work with Microsoft 365 Copilot, the less I think about prompts – and the more I think about permissions. It’s one thing to have an AI that can summarise public docs. It’s a very different thing to plug it into your company’s real data and let people ask whatever they want. At that point, the question isn’t “Can Copilot answer this?” but: “Should Copilot answer this – for this user – right now?” In this post I want to talk about security trimming in the context of M365 Copilot: what it actually means, where people are currently cutting corners, and how I’d implement a practical, generic pattern when you connect external systems like Confluence or custom APIs. I’ll keep it concrete and code-backed, not just policy talk. 1. Why security trimming is not optional with Copilot When people roll out Copilot in a hurry, the conversation often sounds like this: “Let’s connect it to everything, then we see what happens.” “It’s just summarising documents, how bad can it be?” Pretty bad