An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15, 9.0, and 10.0. An attacker can send a PDF document through mail that contains malicious JavaScript. While previewing this file in webmail in the Chrome browser, the stored XSS payload is executed. (This has been mitigated by sanitising the JavaScript code present in a PDF document.)
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy