Copilot and oversharing: clean up SharePoint before you roll out

Recently at a customer, a mechanical engineering company from the Bergisches Land region in Germany, mid-sized, well set up, an IT team of three people for two locations. The assignment: roll out Copilot for Microsoft 365, forty licenses, a pilot group from sales and management. The rollout plan was ready, the training dates were booked.

Then, out of habit, I took a look at the data access governance reports in the SharePoint admin center. Ten minutes later I was sitting with the head of IT in front of an export with more than 600 broad shares. Among them: a salary list from 2021, a folder with customer contracts and a team with internal M&A documents. The team was public. Visible for all 340 employees, including working students.

Copilot would have found at least the M&A team without any detour. Not because Copilot is a security problem, but because it does exactly what it was built for: it searches everything the asking user is allowed to see based on permissions, and presents it in a clean answer. The problem was not Copilot. It was us: three years of sharing sprawl that nobody cleaned up, because “there has never been a problem”.

That is exactly why I am writing this article. This scenario is not an exception, it is the normal case. And governance homework before a Copilot rollout is not a nice-to-have anymore, it is mandatory.

Copilot does not uncover anything new, it makes legacy issues visible

The uncomfortable truth first: Copilot does not create a new risk. Every file Copilot cites in an answer was already accessible to the asking user before, through SharePoint, OneDrive or Teams. What changes is discoverability. Before, somebody had to know that the salary list exists, know the path and open it manually. Now a question like “What do department heads earn on average?” is enough, and Copilot delivers the answer including the source.

Microsoft quite bluntly calls this “oversharing” in its own documentation. Reviewing permissions regularly has always been good practice. Only before Copilot, nobody felt the pressure. Now they do.

The link myth: not every share is equally dangerous

This is worth a close look, because many admins misjudge the situation. A sharing link for “People in your organization” does not, by itself, make a file visible to Copilot. Access only starts when somebody actually clicks the link. A link forgotten in an old email is a sleeping risk at first.

It wakes up in two cases. First, when somebody posts the link in a big Teams channel and hundreds of people click it. Every click creates real access. Second, and this is the much bigger lever: permissions for “Everyone except external users” and public sites. A public site, which is the default, can be found by anyone in the organization, and anyone can open its content. Copilot finds exactly this content without any click beforehand.

Share	What Copilot sees	Priority
Critical — “Everyone except external users” and public sites or teams	All content, for all employees, without any click beforehand	Clean up first
Medium — organization-wide links, widely spread	Content for everybody who clicked the link	Tackle next, especially links in big channels
Low — links for specific people	Only for the explicitly named people	Set as the new default

For your prioritization this means: clean up the broad permissions first, then the links.

Where oversharing typically comes from

From project experience, it is almost always the same four sources.

First, “Everyone except external users”. Years ago somebody added this group to a site or folder because it had to go fast. Since then the whole company sees everything in it.

Second, public teams. A quick project, a team with default settings, and confidential documents are open for everybody. On top come teams whose member list nobody ever touched again, even though the project ended long ago.

Third, broad sharing links. If the default link type is still set to “People in your organization”, new links with far too much reach are created every day. That is why Microsoft recommends switching the sharing settings for SharePoint and OneDrive from organization-wide links to links for specific people. Tenant-wide you do that in the SharePoint Online Management Shell:

# Set the default sharing link for the whole tenant to "Specific people"
Connect-SPOService -Url https://<tenant>-admin.sharepoint.com
Set-SPOTenant -DefaultSharingLinkType Direct

Direct means “Specific people”. Existing links stay untouched, only new ones are created narrower from now on.

Fourth, forgotten guest accounts. Set up for a single workshop, then happily kept running. Guest access does not expire by itself if you do not configure anything.

None of these causes is exotic. These are the same clicks again and again, adding up over the years.

SharePoint Advanced Management: the tool you need now

With SharePoint Advanced Management (SAM), Microsoft built a toolset exactly for this problem. The good news: as soon as at least one user in your tenant has a Microsoft 365 Copilot license, SharePoint admins get access to the SAM features for the Copilot deployment. For you as an admin, three building blocks matter most.

Data access governance reports

You find them under SharePoint Admin Center › Reports › Data access governance. They show you where it is burning. The sharing links report is an activity report: it shows the sites where the most new links were created in the last 28 days. For legacy issues you need the snapshot reports, for example the report that finds all sites, folders and files that are effectively public through “Everyone except external users” or “Everyone”.

Site access reviews

They move the review to where the expertise is. IT delegates the review of overshared sites to their owners. This works for the top 100 sites from the reports. Instead of IT going through 400 sites alone, every owner confirms or corrects their own permissions.

Restricted Content Discovery (RCD)

RCD is your emergency exit. You remove a site from Copilot and organization-wide search without changing the access permissions. Users with access can still open the files directly. This fits cases like HR data that is accessible more broadly internally for good reasons, but should not show up as a Copilot answer. Two things you should know: RCD does not work for OneDrive, and overusing it makes search and Copilot results worse. Also, Microsoft has tightened it: since late July 2026, Copilot and search no longer show files from RCD sites, even if a user recently opened them.

Important for expectations: SAM does not clean up automatically. It shows you where you need to clean up. The actual work, meaning revoking shares, briefing owners and setting labels, stays with you and the business departments.

The role of Microsoft Purview

In parallel to SAM, it pays off to look at Purview, because sensitivity labels and DLP are the second line of defence.

A sensitivity label with encryption ties Copilot to the usage rights. The user needs the EXTRACT and VIEW rights so Copilot can summarize the data. So you can build labels that allow reading, but keep Copilot out.

DLP goes one step further. Since the rollout starting late June 2025, DLP for Microsoft 365 Copilot is generally available and can exclude labeled content from Copilot answers. On top comes a DLP variant that detects sensitive data directly in the prompt. It started as a preview and the feature set keeps growing. Check the current status in your tenant.

I deliberately do not go into every Purview detail here, that is an article of its own. For the Copilot rollout, this rule of thumb is enough: labels are the foundation, DLP is the addition, SAM is the clean-up tool.

Do not forget Teams governance

The focus is often on SharePoint, because that is where the big numbers come from. Teams still deserves its own attention. First check which teams are public and contain confidential content. Private and shared channels have their own SharePoint sites with their own permissions. This regularly leads to surprises, because they are easily overlooked during reviews.

For guest access: Teams itself has no expiration switch. You work with expiration policies for guest access in SharePoint and OneDrive and with Entra access reviews. Access reviews cover all Microsoft 365 groups and teams, but no standalone SharePoint sites. Plan Entra ID P2 or Entra ID Governance for this.

What is new: admin agents as support

Microsoft now brings agents to the governance side as well. With the SharePoint Admin Agent you ask in chat for overshared sites and kick off reviews. Microsoft stresses that the agent analyzes, gives recommendations and runs safe actions, while destructive steps like deleting content stay with the admin.

The direction makes sense: if Copilot speeds up finding data, governance needs speed too. Still: keep an eye on the Message Center. The feature set is growing fast right now, and no agent takes the decision away from you what is really confidential.

The concrete approach before the rollout

In practice, this order has proven itself for us:

I also published a post on this topic on LinkedIn. If you have your own oversharing stories from your tenant, tell me there what showed up when you looked closely for the first time.