A sophisticated cyber espionage campaign leveraging a critical zero-day vulnerability in Microsoft Office has targeted Ukrainian government agencies and European Union institutions, security researchers have confirmed. The threat group UAC-0001, widely tracked as APT28 and attributed to Russian military intelligence, deployed advanced malware payloads through weaponized documents exploiting CVE-2026-21509 within hours of Microsoft’s public disclosure. […] The post Hackers Actively Exploit Microsoft Office Zero-Day to Deliver Malware appeared first on Cyber Security News.