An issue was discovered in Mutt before 1.10.1 and NeoMutt before 2018-07-16. pop.c does not forbid characters that may have unsafe interaction with message-cache pathnames, as demonstrated by a '/' character.
https://www.debian.org/security/2018/dsa-4277
https://usn.ubuntu.com/3719-3/
https://security.gentoo.org/glsa/201810-07
https://neomutt.org/2018/07/16/release
https://lists.debian.org/debian-lts-announce/2018/08/msg00001.html
https://gitlab.com/muttmua/mutt/commit/6aed28b40a0410ec47d40c8c7296d8d10bae7576
https://github.com/neomutt/neomutt/commit/9bfab35522301794483f8f9ed60820bdec9be59e