Just to extend the sibling comment with an excerpt of the Arch announce mail regarding the backdoor:

  >From the upstream report [1]:
  
  > openssh does not directly use liblzma. However debian and several other
  distributions patch openssh to support systemd notification, and libsystemd
  does depend on lzma.
  
  Arch does not directly link openssh to liblzma, and thus this attack vector is not possible. You can confirm this by issuing the following command:
   
   ```
   ldd "$(command -v sshd)"
   ```
   
  However, out of an abundance of caution, we advise users to remove the malicious code from their system by upgrading either way. This is because other yet-to-be discovered methods to exploit the backdoor could exist.