Russian hackers are targeting a new Office 365 zero-day, so patch now

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

Cyberattacks Target Ukraine and EU via Microsoft Office Vulnerability CERT-UA has reported a new wave of cyberattacks targeting Ukrainian government agencies and EU organizations, exploiting the Microsoft Office vulnerability CVE-2026-21509. Attackers are using malicious emails disguised as communications from the Ukrainian Hydrometeorological Center to gain access to victims' systems. 59 sources 50