ACTIVELY EXPLOITED3 sources verified·1 min read
By Lyrie Threat Intelligence·3/18/2026
CVE-2025-66376 added to CISA KEV: Synacor Zimbra Collaboration Suite (ZCS)
Status: ✅ Confirmed exploited in the wild
Date added: 2026-03-18
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Due date: 2026-04-01
Why this matters
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability in the Classic UI where attackers could abuse Cascading Style Sheets (CSS) @import directives in email HTML.
Sources
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