PSA: I just noticed homebrew installed the compromised version on my Mac as a dependency of some other package. You may want to check this to see what version you get:
xz --version
Homebrew has already taken action, a `brew upgrade` will downgrade back to the last known good version.
GitHub disabled the xz repo, making it a bit more difficult for nix to revert to an older version. They've made a fix, but it will take several more days for the build systems to finish rebuilding the ~220,000 packages that depend on the bootstrap utils.
What should they be relying on instead? Maybe rsync everything to an FTP server? Or Torrents? From your other comments, you seem to think no one should ever use GitHub for anything.