Manual:WrapOldPasswords.php/en

Details
wrapOldPasswords.php file is a maintenance script to wrap all passwords of a certain type in a specified layered type that wraps around the old type.

Since MediaWiki 1.24, if using the default settings, password hashes will automatically be updated to PBKDF2 as users log in. This is not working currently. If necessary, the old MD5 hashing can be restored by changing  to ' '.

This maintenance script can wrap all passwords in  or   if you do not want to wait for your users to log in.