CVE-2025-27915
Description
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability 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 <details> 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.
How to fix
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date: Oct 28, 2025- synacor zimbra_collaboration_suite10.0.13, 10.1.5 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| synacor zimbra_collaboration_suite | 10.0.0 ≤ v < 10.0.13, 10.1.0 ≤ v < 10.1.5, 9.0.0 | 10.0.13, 10.1.5 |
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