Disclosure summary
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.
CISA remediation guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
Rapid7 Blog · RSS-087d9d059be8baf7b6734d576c5516c0ae3
Open original source · Updated Sep 24, 2026
When Business Email Compromise Starts Rewriting Reality
CVE mention in publisher metadata; check the original affected versions.
Original records & references
PUBLISHED 2025-10-07T00:00:00-04:00
MODIFIED 2025-10-07T00:00:00-04:00
INGESTED 2026-10-06T11:42:57-04:00