For OS X 10.8-10.13 move passwords out of the way non-destructively.
This will not work on 10.14. There are new user plist protections that prevent this tool from operating as expected. There are no plans to update it.
This is a script I designed to solve the simple problem that people cannot remember their passwords when asked. This tool lets you move the password out of the way–replacing it with a password you choose ("mm" by default in the script). You can then simply put the password back. You don't have to know the password, and as long as there is no FileVault you can do this to any machine.
This script is designed for IT professionals where this can be useful. Please use it as intended.