Steps to reproduce the issue

Could not login to the admin panel for my website, once checked the database, realised all the username/passwords were changed to admin/admin.
Had a backup from a month ago, downloaded a current version of the site to check if the MD5 of the files matched, found nothing suspicious amongst the files. Not sure if it is one incident and something wrong with other services or is it joomla specific. So, I thought I should report it here just to have it looked into even if brief.

Expected result

Actual result

System information (as much as possible)

Modules Installed

NoNumber Advanced
NoNumber Extension
Phoca Font
Adeeba Backup
Easy Frontended SEO
Advanced Module Manager
NoNumber Extension Manager
Content - RokInjectModule

System Info

Database Version 5.5.40-cll
Database Collation utf8_general_ci
PHP Version 5.4.28
Web Server Apache/2.2.27 (Unix) mod_ssl/2.2.27 OpenSSL/0.9.8e-fips-rhel5 mod_bwlimited/1.4
WebServer to PHP Interface cgi-fcgi
Joomla! Version Joomla! 3.3.6 Stable [ Ember ] 01-October-2014 02:00 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
User Agent Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:35.0) Gecko/20100101 Firefox/35.0

Additional comments

There are no other admins on the system, but everyone was made an admin on the system. The number of users were about 10 as the site is mainly about giving information out but it is amongst the 200's websites within the country according to Alexa.

I changed the password and username for the two main admins and deleted the rest. I have also changed the password to the database.