An issue was discovered in Zimbra Collaboration (ZCS) through 10.1. A Cross-Site Scripting (XSS) vulnerability exists in Zimbra webmail due to insufficient validation of the content type metadata when importing files into the briefcase. Attackers can exploit this issue by crafting a file with manipulated metadata, allowing them to bypass content type checks and execute arbitrary JavaScript within the victim's session.
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.9#Security_Fixes