Yet another reason why the xz backdoor is a sneaky b@$tard
A contributor to the liblzma library (a compression library that is used by the OpenSSH project, among many others) submitted malicious code that included an obfuscated backdoor. Since the maintainers had no reason to suspect foul play, they accepted and merged the contribution. The malicious code made it into the compression library release, and later on to the OpenSSH server, which relies on the library in question.