Font's are a very significant attack vector
https://googleprojectzero.blogspot.com/2016/06/a-year-of-windows-kernel-font-fuzzing-1_27.html
How do you ensure your font files are virus/malware free?

Might have found my own answer here;
https://cloudblogs.microsoft.com/microsoftsecure/2017/01/13/hardening-windows-10-with-zero-day-exploit-mitigations/

Until new vulnerabilities are found of course...
https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=font