A stored XSS issue was discovered in DAViCal through 1.1.8. It does not adequately sanitize output of various fields that can be set by unprivileged users, making it possible for JavaScript stored in those fields to be executed by another (possibly privileged) user. Affected database fields include Username, Display Name, and Email.
https://www.debian.org/security/2019/dsa-4582
https://seclists.org/bugtraq/2019/Dec/30
https://lists.debian.org/debian-lts-announce/2019/12/msg00016.html
https://hackdefense.com/publications/cve-2019-18347-davical-caldav-server-vulnerability/
https://gitlab.com/davical-project/davical/blob/master/ChangeLog
http://seclists.org/fulldisclosure/2019/Dec/19
http://seclists.org/fulldisclosure/2019/Dec/18