Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability. Actively exploited: CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on 20/04/2026. Patch affected systems as an emergency.
| Package | Affected versions | Patched versions |
|---|---|---|
| zimbra collaboration suite | = 8.8.15= 9.0.0≥ 10.0.0, < 10.0.12≥ 10.1.0, < 10.1.4 | 10.0.1210.1.4 |
An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0 and 10.0 and 10.1. A Cross-Site Scripting (XSS) vulnerability in the Zimbra Classic UI allows attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. This issue arises from insufficient sanitization of HTML content, specifically involving crafted tag structures and attribute values that include an @import directive and other script injection vectors. The vulnerability is triggered when a user views a crafted e-mail message in the Classic UI, requiring no additional user interaction.
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