Full Report
Microsoft says an ongoing incident is preventing users of its Teams collaboration platform and free Office for the web cloud-based productivity suite from opening files. [...]
Analysis Summary
# Incident Report: Microsoft 365 Service Disruption (Office for the Web & Teams)
## Executive Summary
An ongoing service incident impacted Microsoft 365, specifically preventing users from accessing or opening files via Office for the Web and Microsoft Teams. Initial analysis points to a cross-service configuration issue rather than a malicious cyberattack. Microsoft is currently analyzing telemetry to isolate the root cause and restore full functionality for affected global users.
## Incident Details
- **Discovery Date:** June 1, 2026
- **Incident Date:** June 1, 2026
- **Affected Organization:** Microsoft (Office for the Web, Teams, Excel)
- **Sector:** Technology / Cloud Service Provider
- **Geography:** Global (Impact noted during European peak hours)
## Timeline of Events
### Initial Access
- **Date/Time:** Approximately 10:36 AM (Discovery/Reported)
- **Vector:** N/A (Service Configuration/Technical Failure)
- **Details:** Users reported receiving the error message: "Office Online services aren't available right now."
### Lateral Movement
- **Details:** N/A. This incident appears to be a service-side failure/outage rather than a security breach involving lateral movement.
### Data Exfiltration/Impact
- **Details:** No data exfiltration reported. Impact was limited to **Availability**; users were unable to open files in Excel for the web, Teams, and other Office cloud applications.
### Detection & Response
- **Discovery:** Detected via service telemetry and user reports to the Microsoft 365 Status portal.
- **Response Actions:** Microsoft opened an investigation under incident ID MO1329446, isolated the issue to a "cross-service" dependency, and began reviewing telemetry to initiate remediation.
## Attack Methodology
*Note: Current evidence indicates a technical outage/misconfiguration rather than a malicious actor.*
- **Initial Access:** N/A - Systemic issue.
- **Persistence:** N/A.
- **Privilege Escalation:** N/A.
- **Defense Evasion:** N/A.
- **Credential Access:** N/A.
- **Discovery:** Internal service telemetry.
- **Lateral Movement:** N/A.
- **Collection:** N/A.
- **Exfiltration:** N/A.
- **Impact:** Service disruption (Denial of Service due to internal error).
## Impact Assessment
- **Financial:** Potential SLA credit claims from enterprise customers.
- **Data Breach:** None reported; data integrity remains intact.
- **Operational:** Significant disruption to collaborative workflows; users unable to view or edit cloud-hosted documents.
- **Reputational:** Moderate; follows a series of recent Microsoft 365 outages (MFA setup issues, Teams client launch failures).
## Indicators of Compromise
- **Network indicators:** hxxps[://]admin[.]microsoft[.]com (Official admin notifications)
- **File indicators:** N/A
- **Behavioral indicators:** Error: "Office Online services aren't available right now."
## Response Actions
- **Containment measures:** Isolation of the "cross-service issue" impacting web experiences.
- **Eradication steps:** (Ongoing) Reviewing recent cache and backend configuration changes.
- **Recovery actions:** Failover procedures initiated in related incidents (MFA outage) to stabilize CPU and memory utilization.
## Lessons Learned
- **Key takeaways:** Dependencies between Office for the Web and Teams mean that a single cross-service failure can impact multiple collaboration pillars simultaneously.
- **What could have been done better:** Earlier identification of the impact of backend configuration changes on European peak-time traffic.
## Recommendations
- **Redundancy:** Ensure critical document workflows have offline backups or desktop client alternatives configured.
- **Monitoring:** Enhance granular telemetry focused on cross-service API calls to identify "bottleneck" failures before they result in global outages.
- **Change Management:** Implement stricter "canary" deployment phases for backend service updates to detect cross-platform regressions in non-production environments.