Zimbra has released a security update to address a critical vulnerability in the Zimbra Classic Web Client that could allow malicious actors to compromise user accounts and execute unauthorized code. The company recommends that customers install the latest update to mitigate the threat.
The flaw is a stored cross-site scripting (XSS) vulnerability that could allow an unauthenticated attacker to execute malicious JavaScript in the browser of a user viewing a specially crafted email message.
The problem exists in the Classic Web Client component of Zimbra Collaboration Suite. While no CVE identifier has been assigned yet, Zimbra warned that successful exploitation of the vulnerability would lead to the exposure of mailbox content and settings, as well as session details.
A stored XSS vulnerability occurs when the application stores user-supplied input without proper sanitization and later displays it to other users.
A stored XSS vulnerability occurs when the application stores user-supplied input without proper sanitization and later displays it to other users.
In this case, an attacker could utilize this flaw to deliver specially crafted email messages that would execute arbitrary JavaScript code in the browser of a user who opens this message in the Zimbra Classic Web Client. The malicious script would then steal the victim’s session and potentially access their mailbox content, modify account settings, or perform other actions.
While Zimbra has not reported any confirmed attacks using this vulnerability, several similar XSS flaws in the Zimbra Collaboration Suite have been actively exploited in the past.
While Zimbra has not reported any confirmed attacks using this vulnerability, several similar XSS flaws in the Zimbra Collaboration Suite have been actively exploited in the past.
Attackers have targeted the webmail platform multiple times to hijack the accounts of high-profile organizations, including the Brazilian military, with no success, according to Zimbra. Previously exploited flaws affecting the product are CVE-2025-27915, CVE-2023-37580, and CVE-2024-27443.
Therefore, organizations must ensure they have applied the latest security update to address the newly discovered vulnerability.
Therefore, organizations must ensure they have applied the latest security update to address the newly discovered vulnerability.
The Zimbra Collaboration Suite 10.1.19 release notes mention the fix for the stored XSS in the Classic Web Client. Users must always access the updated version of the webmail platform via HTTPS to avoid man-in-the-middle attacks and other threats.
Moreover, security analysts recommend monitoring the email traffic for any signs of suspicious activity and reviewing account access logs for unauthorized changes.
Moreover, security analysts recommend monitoring the email traffic for any signs of suspicious activity and reviewing account access logs for unauthorized changes.
Users must not open any attachments or links in emails that seem suspicious as these may contain malicious scripts that target webmail clients. Organizations must ensure they apply all security updates to their collaboration platforms as they provide critical protection against potential threats.
In this case, the newly discovered vulnerability is yet another reminder of the importance of timely software updates. Attackers will continue targeting collaboration platforms such as Zimbra webmail to compromise user accounts by exploiting flaws such as XSS.
This article has been indexed from CySecurity News – Latest Information Security and Hacking Incidents
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