These are the steps you need to follow(linux/xampp)
1) go to terminal and type /opt/lampp/bin/mysql -u root -p
2) after that enter the mysql user password if it worked well 
then type exit (if it doesn't have password hit enter without
typing anything)
3)after that type cd /opt/lampp/bin and now type
       sudo ./mysql_upgrade -u root -p 
, enter your password and tadam , here is your mysql upgraded