By default, when upgrading MediaWiki, you have to run the update.php file from a command prompt.

This becomes a problem if you don't have SSH access to your account. Fortunately, there is a way to run the script through your browser. Follow the steps below to complete the process: 

• Rename LocalSettings.php to something else (e.g. LocalSettings-old.php)
• Open your site in the browser and start the installer
• Fill in the fields using the same details (MySQL user, database, password) as the ones for the existing installation
• Start the installation - the install script will detect the existing database tables and upgrade their schema
• Delete the newly-generated LocalSettings.php file
• Rename the old file (LocalSettings-old.php) to LocalSettings.php

This will complete the MediaWiki upgrade.