Microsoft 365 Alert – Service Degradation – Microsoft 365 Defender – Users encounter slow loading webpages in third-party web browsers if utilizing the web content filtering feature – RESOLVED

30/06/2023 09:51:00 AM (GMT)

NHSmail Reference : INC36720713

Microsoft Reference : DZ615064

Issue Status : RESOLVED

Issue Description : Users encounter slow loading webpages in third-party web browsers if utilizing the web content filtering feature.

More info : This only occurs for users that are utilizing version 4.18.23050 of Microsoft Defender for Endpoint’s web content filtering feature. Admins can revert build 4.18.23050 of Microsoft Defender for Endpoint to a previous version on behalf of affected users as a work around by following the steps explained in the link below:

https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/microsoft-defender-antivirus-updates?view=o365-worldwide#how-to-roll-back-an-update

Alternatively, admins can change their network protection settings in the Microsoft 365 Defender portal to audit mode to temporarily remediate impact.

Final Update : 25/07/2023 08:33:00 AM – Microsoft have completed deploying the fix to the impacted environment and confirmed with internal testing and validation that the issue is resolved.

Scope of impact : Any user utilizing version 4.18.23050 of Microsoft Defender for Endpoint’s web content filtering feature is impacted.

Root cause : A recent Microsoft Defender for Endpoint update introduced a code regression in the web content filtering feature that slows third-party web browsers’ ability to open web pages.

Next steps : Microsoft are further reviewing the recent update to identify what prevented the code regression from being detected in our update testing and validation procedures, which will allow them to prevent similar issues in future updates.