Runbook Lab · Security · Updated 28 October 2026 · checked against Microsoft Learn
Copilot doesn't break permissions. It just finds everything your permissions already allow, very quickly. A salary spreadsheet shared with "Everyone except external users" years ago is now one prompt away. Five steps to deal with that first, in the order Microsoft's own Copilot oversharing blueprint uses.
Get the free Top 5 kitMicrosoft 365 hardening checklistSharePoint admin center > Reports > Data access governance: permission state report and the 'Everyone except external users' insights. Add a read-only list of sites that still allow Anyone links:
Connect-SPOService -Url https://<tenant>-admin.sharepoint.com
$s = Get-SPOSite -Limit All |
Where-Object { $_.SharingCapability -eq 'ExternalUserAndGuestSharing' }
"Sites that allow Anyone links: $(@($s).Count)"
$s | Select-Object Url, Title | Export-Csv -NoTypeInformation .\anyone-sites.csvActive sites > site > Settings > 'Restrict content from Microsoft Copilot'. Use it on a short list only: every restricted site makes answers less complete. Write a removal date next to each site.
Policies > Sharing: default link 'Specific people', permission View, and an expiry on Anyone links (or turn them off). This only affects new links.
Get-SPOTenant | Select-Object SharingCapability, DefaultSharingLinkType, DefaultLinkPermission, RequireAnonymousLinksExpireInDays
Start site access reviews from the EEEU report so owners remove it, then hide the claim in the people picker. Expect a few access tickets.
Before the pilot, not after the first incident:
Connect-ExchangeOnline (Get-AdminAuditLogConfig).UnifiedAuditLogIngestionEnabled Search-UnifiedAuditLog -StartDate (Get-Date).AddDays(-7) -EndDate (Get-Date) ` -RecordType CopilotInteraction -ResultSize 100
Restricted Content Discovery hides content from Copilot and organisation-wide search. People with access can still open the files.
Large sites can take over a week to reflect the restriction. Data access governance reports can take hours.
DLP that blocks sensitive data in Copilot prompts was still in preview on 5 October 2026. Labeled-file blocking is the safer start.
The five steps as a guide with impact and rollback per control, a Jira import, a tracker CSV, an Excel project plan and read-only PowerShell checks.
Download freeThe M365 Hardening Kit covers identity, email, Teams, SharePoint and monitoring in 58 controls, including Copilot oversharing basics.
See the Complete kitNo. Copilot only uses content the signed-in user already has permission to open. The risk is oversharing: files shared with 'Everyone except external users', company-wide links or broken inheritance that nobody noticed before Copilot made them easy to find.
A SharePoint Advanced Management setting that keeps a site's content out of organisation-wide search and Copilot answers while you fix its permissions. It does not change permissions, works on SharePoint sites only (not OneDrive), and sites with more than 500,000 items can take over a week to reflect the change. Microsoft calls it an interim protection.
Microsoft Learn says SharePoint Advanced Management is included with Microsoft Copilot licences. Purview capabilities depend on your plan: foundational features are in Microsoft 365 E3, optimised ones in E5 or E7.
Yes, a DLP policy for the Microsoft 365 Copilot and Copilot Chat location can block processing of files and emails with chosen sensitivity labels. Blocking sensitive information types in prompts was still in preview on Microsoft Learn (5 October 2026).
Yes. Copilot interactions are logged in Audit (Standard) under the CopilotInteraction record type, provided auditing is turned on in your tenant. Search them in Microsoft Purview > Audit.