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If you look closely inside the archive, the files are supposed to be extracted to specific folders in your XOOPS installation
mysqldatabase.php to class\database
error.php to modules\system\language\english
error.php to root
just extract the hotfix archive in your root XOOPS directory installation, the necessary files should automatically be extracted to those folders.
then don't forget to run xoopsupdate.php
hth.
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