Από το Siteground
https://www.siteground.com/kb/How_to_reset_my_Joomla_administrator_password/
How to reset my Joomla! administrator password?
Change your Joomla! administrator password through phpMyAdmin by using the steps below:
- Access your phpMyAdmin in Site Tools and select the Joomla! database from the drop-down menu on the left;
- Select the users table (e.g. jos_users);
Προσοχή!Στη βάση μπορεί να υπάρχουν πίνακες από παλαιότερη έκδοση του Joomla.Επιλέξτε τους πίνακες της τρέχουσας εγκαταστημένης έκδοσης. - Click Browse and select Edit (the small pen icon) on the user;
- Under the “password” field, you will see encrypted letters. Delete these letters, and type your new password;
- Select MD5 in the Function drop-down list on the left side of the password field;
- Save your new password and access your Joomla! administrator backend.