This indicates an attack attempt against a Cross-Site Request Forgery vulnerability in Zimbra Collaboration.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. An attacker may exploit this to cause the server to perform certain actions in the context of an authorized user's session and gain unauthorized access to the affected application.
Zimbra Collaboration before 8.7.11 patch 2 and 8.8.8 patch 1.
Cross-Site Request Forgery
Apply the latest update from the vendor.