Executive summary
Public evidence documents CVE-2025-27915. This report does not assess any organization.
Technical analysis
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's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
IOCs
No public IOC is available.
CVEs and affected products
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
ATT&CK mapping
No ATT&CK mapping is available.
Detection content
Sigma rules, YARA rules, Splunk SPL, and KQL detection logic.
Threat hunting
Hypothesis-driven hunt procedures and telemetry checklist.
Remediation
Containment actions, patching notes, and credential steps.
Historical relationships
No published historical relationship is available.
Timeline and change history
Confidence and caveats
1.0
⚠️ Public CTI only; no organizational exposure is asserted.
⚠️ CVSS and EPSS metadata were not present in the retrieved evidence payload.
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Intelligence Sources & Advisory Feeds
DFIR investigations, vendor research, advisory feeds & verified claims
1 reference
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Public evidence for CVE-2025-27915 with preserved provenance.
CVE-2025-27915 Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability 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's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.