In wordpress if you receive either of the following errors when trying to upload a theme...
"Are you sure you want to do this?"
Add the following code to your public_html/.htaccess file...
php_value upload_max_filesize 64M
php_value post_max_size 64M
php_value max_execution_time 300
php_value max_input_time 300
If the public_html/.htaccess file does not exist, be sure that you have "View hidden files" enabled in your File Manager's settings. Then create the .htaccess file if it does not show. Then add the code.