I can search post with ' in quick search box.
' is smaller than the minimum length "2" I set. but ' Ignores the rule.
Is it a bug? Is it vulnerable to security?
I'm unable to reproduce this. What version of MyBB are you using? Have you made any core edits? I would of opted and said your database search length requirement could of been reduced, but the search string is checked through PHP first so the database length requirement is irrelevant.
this is my test site I just made.
I didn't edit any codes. I just down 1817 and install it.
I set Minimum Search Word Length '2'
Other character like " or ! are not searched. except '
try search ' in quick search box
Should I change minimum length from 2 to 3 ?