Summary：**Alarming Zimbra Bug Allows Hackers to Run Malicious Code in Your Inbox** *Zimbra urges immediate

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**Alarming Zimbra Bug Allows Hackers to Run Malicious Code in Your Inbox**
*Zimbra urges immediate patching after a stored XSS flaw in the Classic Web Client enables arbitrary code execution.*

**Introduction**
Enterprise email administrators are on high alert after Zimbra disclosed a critical vulnerability affecting its Classic Web Client. Tracked as CVE‑2024‑XXXX, the flaw is a stored cross‑site scripting (XSS) issue that lets an attacker inject malicious scripts into a user’s mailbox. Once executed, the script can run arbitrary code in the victim’s browser, potentially leading to credential theft, data exfiltration, or further network compromise. Zimbra has rated the vulnerability as “critical” and is pushing customers to apply the latest security update without delay.

**Key Developments**
The bug was discovered by an independent security researcher who reported it through Zimbra’s bug‑bounty program in early September. Analysis revealed that the vulnerability stems from insufficient sanitization of HTML content rendered in the email preview pane. When a specially crafted message—containing a malicious payload hidden in an attachment or inline HTML—is opened, the script persists in the client’s storage and executes each time the preview loads. Because the attack is stored, it does not require the victim to click a link; merely viewing the infected email triggers the exploit. Zimbra released version 8.8.15 Patch 4 on September 22, which includes input‑validation fixes and a revised Content Security Policy (CSP) to block inline scripts. The company also advised administrators to disable the Classic Web Client’s preview feature as a temporary mitigation until patches can be applied.

**Industry Analysis**
Stored XSS remains one of the most dangerous