Microsoft Defender for Office 365 Misidentifies Google Search URLs as Threats

Microsoft has opened an investigation after its Defender for Office 365 service began flagging ordinary Google search links as malicious, temporarily preventing users from opening the URLs in email messages.

Defender for Office 365 is the cloud‑based component of Microsoft’s broader security suite that scans incoming and outgoing email for phishing, malware and unsafe links. When a link is deemed suspicious, the service redirects the user to a warning page or blocks access entirely, a safeguard meant to stop credential theft and drive‑by attacks.

The problem first came to light through a report on BleepingComputer, which detailed instances where recipients of legitimate Google search URLs received security warnings instead of reaching the intended results page. Affected users described the behavior as a “false positive,” noting that the URLs in question were standard search queries generated by the Google search engine.

While the issue appears limited to Google search links, its impact could be significant for organizations that rely heavily on email for sharing research, support tickets, or collaborative links. A blocked link can disrupt workflows, cause confusion, and potentially erode confidence in the email security layer if legitimate content is repeatedly denied.

Microsoft’s response has been to acknowledge the false positive and to prioritize a fix. In a brief statement, the company said engineers are reviewing the detection logic that triggered the block and that administrators can monitor the situation through the security console. The firm also advised administrators to temporarily whitelist the affected URLs or to use the “report false positive” feature while a permanent solution is developed.

False positives are a known challenge for any automated security solution, which must balance aggressive threat detection against the risk of impeding normal user activity. Security experts note that the incident underscores the importance of keeping detection rules up‑to‑date and of providing clear channels for users to report erroneous blocks. Microsoft is expected to roll out an update to Defender for Office 365 in the coming weeks, aiming to restore normal access to Google search links without compromising overall protection.