Search for the regex "\$wp_version =" in all the regular files that end with '/wp-includes/version.php' (case insensitive) in their paths in directories/files taken from the glob pattern '/var/www/vhosts/*/httpdocs' and show the matched lines along with the file names
find /var/www/vhosts/*/httpdocs -type f -iwholename "*/wp-includes/version.php" -exec grep -H "\$wp_version =" {} \;