The Zimbra Collaboration suite's Classic Web Client contains a critical XSS vulnerability. This flaw enables attackers to inject and execute arbitrary scripts within the web client interface. The vendor has issued an advisory urging customers to patch the vulnerability, though no explicit patch or version details are provided in the current data. The vulnerability is classified as critical due to the potential impact on client-side security.

Successful exploitation of this XSS vulnerability could allow attackers to execute arbitrary scripts in the context of the Classic Web Client, potentially leading to session hijacking, credential theft, or other malicious actions within the user's browser session. However, no known exploits in the wild have been reported at this time.

Zimbra has urged customers to apply available patches to remediate this critical XSS vulnerability. Since no specific patch links or version information are provided, customers should consult the official Zimbra security advisories or vendor communications for the latest patch and remediation instructions. Patch status is not yet confirmed in the provided data—check the vendor advisory for current remediation guidance.