Copilot Exposes SharePoint Oversharing: Fix Permissions First

It takes no exploit, no stolen credentials and no malicious code. A plain-language question to Copilot is all it takes to open a confidential file in a Microsoft 365 tenant.

A Copilot readiness assessment that Brennan ran this year for a professional services firm shows how. The case is described in a sponsored piece on iTnews^[1] published on October 14, 2026. The firm scored strong in four areas and weak in two: information classification and data governance.

A well-run firm with two blind spots

The four strong areas were:

• Microsoft 365 adoption;
• content consolidated in a single location;
• SharePoint architecture;
• user readiness.

The firm used SharePoint as its main document repository. According to the report, its sharing settings allow users to discover files they can technically access but would normally never go looking for.

The wider context comes from ADAPT, which the same piece cites. ADAPT's April 2026 research covered more than 200 data and technology leaders in Australia and New Zealand. It found that roughly half of the AI tools in pilot or in use sit outside a formal governance framework. Only 8% of Chief Data Officers say their organization's data is ready for AI.

The sample covers Australian and New Zealand companies, so organizations elsewhere, Italian firms included, need to measure their own numbers in-house.

Ask a question instead of searching

Copilot honors every permission already set in Microsoft 365.

It returns to each person only the content that person is entitled to see. The authorization gaps are the same ones that were already there.

Until now, a misconfigured permission stayed harmless for a practical reason. To open the file, you had to know it existed. You also had to have a rough idea of where it lived.

Copilot removes both conditions. A curious user needs no knowledge of the folder structure, no extra privileges and no hostile intent.

Brennan's report says it plainly: Copilot amplifies permission problems that already exist.

Broad permissions were dormant technical debt

The root cause is access granted for convenience and never revoked. The review Brennan proposes looks for three common patterns:

• organization-wide permissions;
• anonymous sharing links;
• collaboration spaces that are more open than intended.

For years this debt cost next to nothing, because the effort of searching acted as a security control. That control never appeared in any risk register.

AI agents follow the same pattern. On dev.to^[2], a developer describes how a single harmless permission granted to his agent became a backdoor for everyone.

When an exposed file contains personal data, the issue lands with the Garante privacy (Italy's data protection authority). Liability stays with the company that set the permissions.

Three checks before the first license

1. Which SharePoint, OneDrive and Teams sites currently have organization-wide permissions or active anonymous links?
2. Does the Unified Audit Log capture file access, sharing and permission changes?
3. Which content carries a sensitivity label, and who assigns it?

Remediation comes before the contract

Brennan puts the permissions review in the first of five phases: Enable, Protect, Direct, Apply, Automate. Enable covers the permissions review and the audit log check.

Organizations that run Enable in parallel with the rollout end up switching Copilot on in a tenant whose gaps are still open.

The case points to four concrete steps:

• tie license activation to the outcome of the review, site by site;
• ask the vendor to start the license term once remediation is complete;
• turn on and test the audit log before the first user goes live;
• open Copilot to a pilot group working on sites that have already been cleaned up.

Copilot is ready for production. Many tenants are not.