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Russian-aligned threat actor TA488, also known as Void Blizzard and Laundry Bear, exploited a previously unknown vulnerability in Zimbra Collaboration Suite mailservers for at least five months during 2025. The vulnerability, later assigned CVE-2025-66376, was leveraged through half-click exploits embedded in HTML emails that executed upon opening without requiring user interaction. Upon successful exploitation, TA488 deployed ZimReaper malware to establish persistent access, steal credentials and two-factor authentication codes, and exfiltrate emails via DNS tunneling and HTTP requests. The campaigns primarily targeted Ukrainian government entities, alongside U.S. government, nuclear science facilities, and defense industrial base organizations. The actor used domains spoofing Zimbra telemetry services and regularly updated obfuscation techniques to evade detection. TA488 is believed to be a private contractor working for Russian intelligence services.
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