The autocmd feature in window.c in Vim before 8.1.2136 accesses freed memory.
https://usn.ubuntu.com/4309-1/
https://packetstormsecurity.com/files/154898
https://github.com/vim/vim/compare/v8.1.2135...v8.1.2136
https://github.com/vim/vim/commit/ec66c41d84e574baf8009dbc0bd088d2bc5b2421