Input bug about 'Korean10key's in IOS (EAGLView::insertText)

I’m client programmer in Korean game company.
I recently received a bug report.

IOS support the ‘10Key’ Korean keyboard since IOS 7.0 OS.
A bug occurs in it.

When you press a key in the ‘CCLabelTTF’, a subscript key, ios recognizes the combination of keys with a superscript character, but Within the cocos2d insertText there arises a problem that the two character recognition. So, the input buffer is a mess.

This phenomenon occurs in all versions of cocos2d-x.
Now, It fixed a temporary but it seems need a fix at the library level.

Need help on how to fix it.

Thank you.