Microsoft is investigating an issue causing the Defender for Office 365 security software to mistakenly block access to legitimate Google search links. [...]
Microsoft Defender suddenly chases harmless Google links instead of viruses and locks users out of their own search. A classification error in "Safe Links" ensures that completely normal Google URLs are marked as malware. Microsoft is working on a solution. (Continue reading)
It is a malfunction that is likely to spread the mess for the users concerned. Microsoft Defender starts blocking legitimate Google search links by identifying them as threats.