CVE-2025-27915 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Overview
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim'...
Vulnerability details
- CVE ID
- CVE-2025-27915
- Vulnerability
- Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
- Vendor
- Synacor
- Affected products
- Synacor: Zimbra Collaboration Suite (ZCS)
- Severity
- HIGH
- Exploitation status
- Actively exploited in the wild (CISA KEV)
- Published
- 2025-10-07
Remediation guidance
CVE-2025-27915 is in CISA's Known Exploited Vulnerabilities (KEV) catalog — U.S. federal civilian agencies are required to remediate it under Binding Operational Directive 22-01. Treat it as a priority for every environment.
Apply the vendor's official security update for Synacor the affected product as soon as possible. Where a patch is unavailable, apply vendor mitigations or isolate/segment exposed systems.
Hunt for indicators of compromise tied to this vulnerability and confirm logging/EDR coverage on affected assets.
Authoritative references
Remediate CVE-2025-27915 — and stay ahead of the next one
CVE-2025-27915 is listed in the CISA KEV catalog as actively exploited — treat remediation as urgent. Scan your domain free to see whether CVE-2025-27915 and other Synacor issues affect you and get a prioritized remediation report (full report from ₹999) — or stream the full feed of 1,600+ actively-exploited CVEs straight into your SOC.
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