NixOS/nixpkgs — pull request #1724 by ttuegel (2014-02-10 14:20:58+00:00)
Title: Properly escape passwords sent to chpasswd

The mutableUsers feature uses `chpasswd` to set users passwords.
Passwords and their hashes were being piped into the program using
double quotes ("") to escape. This causes any `$` characters to be
expanded as shell variables. This is a serious problem because all the
password hash methods besides DES use multiple `$` in the hashes. Single
quotes ('') should be used instead to prevent shell variable expansion.