Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams
ID: MO1148487
Issue type: Incident
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Impacted services
Microsoft 365 suite
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Details
Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams
User impact: Users may have been blocked from opening URLs in Exchange Online messages and Microsoft Teams.
More info: Additionally, admins may have received alerts titled "A potentially malicious URL click was detected involving one user"; however, the URLs were confirmed as safe.
Some email messages may have also been incorrectly quarantined.
Final status: After an extended period of monitoring, we've confirmed that the service remains healthy and users will no longer experience impact.
Scope of impact: Any user receiving email messages or messages within Microsoft Teams containing specific URLs may have been affected.
Start time: Friday, September 5, 2025, at 1:10 PM UTC
End time: Tuesday, September 9, 2025, at 8:46 PM UTC
Preliminary root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.
Next steps:
- We're further reviewing why the anti-spam service incorrectly flagged the affected URLs to prevent similar issues from happening in the future.
We'll provide a preliminary Post-Incident Report within two business days and a final Post-Incident Report within five business days.
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