If you are using pretty permalinks, you may have noticed WordPress sanitizes it removing accents and some special characters.
However some of these characters are not sanitized by default, meaning they can be added to some of your post URLs, like a trademark symbol(®), a copyright symbol(©) or even a UTF-8 symbol like ⛓.
Although it may not hurt you at first, it may let users confused and it can cause some problems when interacting with some third party API that is not prepared to read such characters.
This plugin Removes special characters from permalinks.
How to use it?
All you have to do is saving/updating your post and you will notice special characters will be swiped out from the permalink.
No screenshots provided