A CSRF issue was discovered in DAViCal through 1.1.8. If an authenticated user visits an attacker-controlled webpage, the attacker can send arbitrary requests in the name of the user to the application. If the attacked user is an administrator, the attacker could for example add a new admin user.
packetstormsecurity.com/files/155629/DAViCal-CalDAV-Server-1.1.8-Cross-Site-Request-Forgery.html
seclists.org/fulldisclosure/2019/Dec/17
seclists.org/fulldisclosure/2019/Dec/18
seclists.org/fulldisclosure/2019/Dec/19
gitlab.com/davical-project/davical/blob/master/ChangeLog
hackdefense.com/publications/cve-2019-18346-davical-caldav-server-vulnerability/
lists.debian.org/debian-lts-announce/2019/12/msg00016.html
seclists.org/bugtraq/2019/Dec/30
www.davical.org/
www.debian.org/security/2019/dsa-4582