These users are created solely for the purpose of gaining access to your website application. You might create users to log into your WordPress, Joomla, or MediaWiki site, for example.
Resetting the password
The unique program you’re using to host the website allows you to reset these user passwords.
The following are some links to external sites for the program you’re using:
Password recovery for WordPress
Password recovery for Joomla
How to Reset Your MediaWiki Password