Security & governance

Why Copilot shows people files they shouldn't see, and what to fix first

By Matteo Garoli 7 min read

A white outline folder with a small person badge on a frosted glass tile, floating over soft amber and ice blue light on a near-black background.

Microsoft 365 Copilot, which Microsoft now calls Microsoft Copilot, can only show a person what that person is already allowed to open. Microsoft says so plainly in its privacy documentation. When a company worries that Copilot will expose confidential files, the files it has in mind are usually ones that people could already open.

I work as a Microsoft 365 Copilot Cloud Solution Architect. This year I’ve run Copilot security and adoption reviews with large organisations in the UK and across Europe. In the security reviews, identity was often in decent shape, and the surprises came from the permissions on the content underneath.

Can Copilot show people files they shouldn’t see?

Yes, when those people already have access to the files. Copilot doesn’t get around permissions. Microsoft’s documentation says it only surfaces organisational data that the individual user has at least view permission to, and that it relies on the same access controls as the rest of Microsoft 365.

Copilot does make those files much easier to find. Picture a spreadsheet of salaries saved years ago on a team site that half the company can technically open. It stayed private because nobody knew it was there. With Copilot, one question in plain English can pull it into an answer, even though the sharing mistake is years older than the licence.

When someone reports that Copilot leaked a document, start by checking who gave that person access to it, and when.

Where does the oversharing come from?

Mostly from decisions that made sense at the time. A project site was created as public because it was quicker, or a folder was shared with the whole company so new starters could find a template. Groups that began with eight people grow to eight hundred, and site owners leave without anyone taking their place.

Public sites and “Everyone except external users” do the most damage. Microsoft’s documentation explains that making a SharePoint site public puts all of its content in front of everyone in the organisation, and that sharing a file or folder with “Everyone except external users” gives access to all current and future employees. Anything shared that way can turn up in anyone’s Copilot answer.

Sharing links work differently, and teams often treat them as the same problem. A “People in your organization” link doesn’t make a file visible to the whole company in search or in Copilot. According to Microsoft’s page on shareable links (updated August 2026), a person has to redeem the link, by clicking it while signed in, before the file becomes accessible to them. People who receive the link directly from SharePoint, OneDrive, Outlook or a Teams chat count as having redeemed it automatically, up to 100 recipients. A “Specific people” link is the opposite case: the file appears in search and in Copilot for everyone added to it. Organisation links can still be forwarded, so they’re worth cleaning up, but I deal with public sites and “Everyone except external users” shares before them.

How common is the problem?

Common enough to slow rollouts down. In a Gartner survey of 132 IT leaders in June 2024, reported by Computerworld, concerns about oversharing led 40% of them to delay their Copilot rollout by three months or more. More recently, ShareGate surveyed 851 IT leaders in the US, Canada, the UK and four EU countries, and in April 2026 reported that 29% said AI tools had already surfaced sensitive internal data, with another 8% unsure. ShareGate sells governance tools and the Gartner data is two years old, so I read both as rough indicators.

You may also come across the claim that 16% of business-critical data is overshared. I don’t use it. It comes from a Concentric AI press release of February 2023, based on 2022 data, and it still gets quoted as if it were new.

What I see in reviews lines up with the surveys. At one payments company, authentication, privileged access, devices and sensitivity labels were all in place. The gaps were in roles and responsibilities, data retention, oversharing and incident procedures. We closed with 47 recommendations, about half of them on data and privacy. I’ve met that combination of strong identity and weak data governance more than once.

Does blocking Copilot fix it?

No. Turning Copilot off, or hiding sites from it, leaves the access where it was. Search and forwarded links can still reach the same files, so blocking Copilot only removes the tool that made the problem easy to see. The same goes for limiting the rollout to a safe group: in the Gartner survey above, 57% of respondents managed the risk by giving Copilot only to “low-risk or trusted” users. That buys time, and the permissions underneath stay as they were.

Microsoft’s own containment tools are built as temporary measures. Restricted Content Discovery keeps selected SharePoint sites out of organisation-wide search and Copilot while people keep the access they already had, and Microsoft describes it as a control to use while permissions are reviewed. It works on SharePoint sites, not on OneDrive, and it can take a while to apply: Microsoft notes that a site with more than 500,000 items may need over a week. The older option, Restricted SharePoint Search, is being retired, and since 31 July 2026 it can no longer be newly switched on.

When I use these controls, I give each site a date by which it should come out of them.

What should you do first?

Microsoft’s current deployment guidance for Copilot, the “Secure & Governed Data Foundation” (May 2026), rests on three pillars: remediate oversharing, set up guardrails, meet regulations. I follow the same order. In practice the first two break down into five steps:

  1. Find the riskiest sites. Microsoft Purview Data Security Posture Management runs a default data risk assessment every week on the 100 most used SharePoint sites. The data access governance reports in SharePoint Advanced Management list sites shared with “Everyone except external users”, sharing links and permission states. SharePoint Advanced Management is available once at least one Copilot licence is assigned in the tenant, so most organisations preparing a rollout already have it; a few features still need the separate add-on.
  2. Contain what can’t be fixed this week by applying Restricted Content Discovery to the sensitive sites that need more time.
  3. Fix the access. Remove “Everyone except external users” where it isn’t needed, make public sites private where they shouldn’t be public, give every site an owner, run site access reviews and repair broken inheritance. Sensitivity labels on sites help the result stay in place.
  4. Lift the temporary controls once a site is clean, so people can use Copilot on it.
  5. Stop the problem coming back. Set secure defaults for new sites, limit company-wide groups and Anyone links, and add data loss prevention policies for Copilot.

Most of this is permissions work that many organisations were putting off long before Copilot arrived. A rollout date tends to bring it back onto the plan.

Who needs to be in the room?

The people who own the data and the security decisions. That sounds obvious, and I’ve still seen it skipped.

At an industrial group, the security leads weren’t there when the review started, so some answers came from people who didn’t look after those areas. On data protection, one participant said it was switched off and another said it was on. At an organisation in the financial sector, the team changed three answers they had given beforehand once a more technical colleague joined the call. Their access perimeter was strong and their governance was thin.

A permissions review run only by the Copilot project team tends to stop where that team’s visibility stops. Bring in whoever owns SharePoint, identity, information protection and compliance, and agree early who decides when a site gets locked down.

If you’re preparing a Copilot rollout and want a second opinion on the permissions side, write to me.

Sources

If you are working on Copilot adoption, a training or a talk, or you are starting out in this world, write to me.