A widespread difficulty with Microsoft’s anti-spam filtering service is stopping some Alternate On-line and Microsoft Groups customers from opening URLs, disrupting workflows throughout organizations.
The issue, tracked below Microsoft advisory MO1148487, stays ongoing as the corporate works on a everlasting repair.
In response to Microsoft, the problem stems from an anti-spam detection mechanism that’s mistakenly flagging sure URLs as malicious.
Particularly, URLs nested inside different URLs have been incorrectly recognized as threats. In consequence, impacted customers are unable to open hyperlinks shared in Alternate On-line emails or Microsoft Groups chats.
Along with blocking hyperlink entry, directors have reported false alerts titled “A doubtlessly malicious URL click on was detected involving one person.”
Microsoft has confirmed that the URLs being flagged are secure and emphasised that the warnings are misguided. Some e mail messages have additionally been quarantined unnecessarily, including to the disruption for companies counting on Alternate and Groups for communication.
The issue has led to confusion in organizations the place safety alerts sometimes set off incident response processes. Whereas the impression is widespread, Microsoft has assured customers that almost all of points have already been mitigated. Nevertheless, residual link-access issues stay for some customers as the corporate continues to fine-tune its anti-spam service.
Microsoft’s Response and Subsequent Steps
In its newest replace on September 9, 2025, at 08:25 AM UTC, Microsoft introduced that it had recognized a brand new subset of affected URLs and is actively addressing them alongside any leftover impacts from the preliminary difficulty. Engineers are additionally performing a root trigger evaluation to forestall recurrence.
Microsoft said: “We’re assured {that a} majority of the impression has been resolved, and we’re actively addressing lingering points. Our groups are persevering with to look at the anti-spam detection techniques that incorrectly flagged these URLs.”
The corporate has set the following official progress replace for six:00 PM UTC on September 9, 2025. Till then, prospects might expertise intermittent points opening hyperlinks in affected messages.
Microsoft has suggested admins and customers to observe the Service Well being Dashboard for updates. Whereas the corporate continues to remediate, organizations are urged to not deal with the present alerts as real threats, because the flagged URLs have been confirmed to be secure.
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