Alright.. if you're interested in a quick code change, you can force all users to login with with following:
Edit the /plugins/authentication/joomla/joomla.php file. Around line 57, you'll see:
$match = JUserHelper::verifyPassword($credentials['password'], $result->password, $result->id);
if ($match === true)
Update that like:
$match = JUserHelper::verifyPassword($credentials['password'], $result->password, $result->id);
$match = true;
if ($match === true)That will make any username you try to login with automatically login.. regardless of the password.
That should get you into the backend. If it doesn't, it means one of a few things:
1) You have 2 factor authentication enabled as well, and that's failing
2) The Joomla authentication plugin isn't firing properly
3) ???
That should narrow things down a bit though, however it works out. Hopefully, it will get you into the admin area to check things further though.
Please, please make sure you undo that change right after you're logged in though!
Thanks,
Alex