Microsoft Defender for Office 365 mistakenly flags Google search links as malicious

Microsoft is investigating an issue where its Defender for Office 365 security software is incorrectly identifying legitimate Google search links as malicious. Users attempting to access these links are encountering "Opening this website might not be safe" warnings, preventing them from proceeding. This problem is causing disruptions for users and may generate related alerts for IT administrators within Microsoft's security solutions, as reported by Bleeping Computer.

The false positive is attributed to an inaccurate security classification within the Defender for Office 365 Safe Links feature. This feature is designed to protect users by rewriting URLs in emails and other Office 365 applications and verifying them at the time of click. However, in this instance, it is erroneously blocking access to valid Google search results. While Microsoft has not specified the number of affected customers or regions, it has categorized the issue as an advisory, suggesting a limited scope.

This is not the first time Microsoft Defender has experienced such false positive incidents; similar issues have occurred in the past with Exchange Online, where legitimate emails were flagged as spam or phishing, or even quarantined. The company is actively working to correct the misclassification and restore normal functionality for affected users.

Source: Bleeping Computer