LibreOffice before 5.4.5 and 6.x before 6.0.1 allows remote attackers to read arbitrary files via =WEBSERVICE calls in a document, which use the COM.MICROSOFT.WEBSERVICE function.
https://www.libreoffice.org/about-us/security/advisories/cve-2018-1055/
https://www.exploit-db.com/exploits/44022/
https://www.debian.org/security/2018/dsa-4111
https://usn.ubuntu.com/3579-1/
https://github.com/jollheef/libreoffice-remote-arbitrary-file-disclosure