PLEASE. I keep seeing it in memes. As I understand it the latest version of the xz package (present in rolling release distros like Arch and SUSE Tumbleweed) has “a backdoor”, but I have no earthly clue what can be done by malicious folks with access to that backdoor or if I should be afraid or how to check if my distro is compromised or how to prevent damage if it is or (…)
TL;DR: Simply downgrade to a version before 5.6.0, or follow the official recommendations for your distro. For Arch, for example, simply upgrade your system.
Explanation (from my understanding ): a malicious developer snuck a backdoor into xz, starting with version 5.6.0,and thankfully it was caught before it could do much damage. This seems to only affect Fedora and Debian based distros, or otherwise distros where ssh is patched to link to systemd, which in turn links to xz. Arch doesn’t seem to be affected, but they took some preventative action. Again, follow the announcements from your distro, or just downgrade xz.
It is not yet clear what a malicious actor can do with that backdoor, but it seems, in affected systems, it enables remote code execution (if you don’t know what that means, just know it’s really bad), but last I checked security researchers were still analyzing the code. Things move fast, so maybe by now it is known.