An issue was discovered in NeoMutt before 2018-07-16. newsrc.c does not properly restrict '/' characters that may have unsafe interaction with cache pathnames.
https://www.debian.org/security/2018/dsa-4277
https://neomutt.org/2018/07/16/release
https://lists.debian.org/debian-lts-announce/2018/08/msg00001.html
https://github.com/neomutt/neomutt/commit/9bfab35522301794483f8f9ed60820bdec9be59e