Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Some email messages may have also been incorrectly quarantined.

Current status: We're continuing to analyze samples of URLs that are seeing continued impact to determine if any additional actions are needed to fully alleviate impact.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Start time: Friday, September 5, 2025, at 1:10 PM UTC

Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.

Next update by: Saturday, September 6, 2025, at 5:00 PM UTC

Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Some email messages may have also been incorrectly quarantined.

Current status: Our efforts to unblock and reprocess the impacted URLs have completed, yet when analyzing the telemetry we've detected a few errors that indicate that some of the URLs may not have completed this process as anticipated. We're analyzing samples of URLs that are seeing continued impact to determine if any additional actions are needed to fully alleviate impact.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Start time: Friday, September 5, 2025, at 1:10 PM UTC

Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.

Next update by: Saturday, September 6, 2025, at 9:00 AM UTC

Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Some email messages may have also been incorrectly quarantined.

Current status: Our unblocking action is taking longer than anticipated. We're continuing to monitor as it progresses to ensure impact is remediated.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Start time: Friday, September 5, 2025, at 1:10 PM UTC

Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.

Next update by: Saturday, September 6, 2025, at 5:00 AM UTC

Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Some email messages may have also been incorrectly quarantined.

Current status: Our unblocking action is progressing as expected and we anticipate that all affected messages should be remediated by the next scheduled communications update.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Start time: Friday, September 5, 2025, at 1:10 PM UTC

Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.

Next update by: Saturday, September 6, 2025, at 1:00 AM UTC

Title: Some users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams

User impact: Users may be blocked from opening URLs in Exchange Online messages and Microsoft Teams.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Some email messages may have also been incorrectly quarantined.

Current status: Our investigation has identified that an anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact. We've identified over 6,000 URLs that are affected and are working to unblock them before replaying messages to recover any messages or URLs that were incorrectly flagged.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Root cause: An anti-spam service incorrectly flagged URLs contained within other URLs as potentially malicious, resulting in impact.

Next update by: Friday, September 5, 2025, at 10:00 PM UTC

Title: Some users may be blocked from opening URLs in Exchange Online messages

User impact: Users may be blocked from opening URLs in Exchange Online messages.

More info: Additionally, admins may receive alerts titled "A potentially malicious URL click was detected involving one user", however the URLs have been confirmed as safe.

Current status: We're reviewing provided email messages containing affected URLs to assist in the investigation and determine our next steps.

Scope of impact: Any user receiving email messages containing specific URLs may be affected.

Next update by: Friday, September 5, 2025, at 8:30 PM UTC