An issue was discovered in Zimbra Collaboration (ZCS) through 10.1. A reflected Cross-Site Scripting (XSS) issue exists through the Briefcase module due to improper sanitization of file content by the OnlyOffice formatter. This occurs when the victim opens a crafted URL pointing to a shared folder containing a malicious file uploaded by the attacker. The vulnerability allows the attacker to execute arbitrary JavaScript in the context of the victim's session.