ServerAuth freeze server!

I found out a ServerAuth glich, /register and some symbol that result. � , is used by players to freeze server!

I used command tracker and made passwords visible and monitored my server!
A players used this command:
/register �password��password�

After that the server freeze for 20 seconds or more

Is there a way to avoid that?

Edit the code to block these symbols

I did with strstr , and didnt get detected ;-; ! Can php block that unknown symbol?

htmlspecialchars() on register and login

Ik that , but i dont know what php commands works on pocketmine!
Normal session are acting strange btw xd !
Thanksssss

Wont work, this is for html , unknown symbol will still show ;-; ! Dang i forgot it