What we know about the xz Utils backdoor that almost infected the world

A backdoor was intentionally planted in xz Utils, a compression library present on almost all Linux and Unix-like systems, and it nearly reached Debian and Red Hat before being spotted. Andres Freund, a Microsoft developer, discovered it after noticing SSH logins consuming too many CPU cycles and producing valgrind errors, and disclosed it on the Open Source Security List. The article says that malicious versions 5.6.0 and 5.6.1 modified sshd through liblzma's link via systemd, and that the attacker, using the name Jia Tan, gained maintainer involvement starting in January 2023. HD Moore, a reverse-engineer, said the final stages activated only on amd64 builds for Debian or Red Hat packages.