MyBB question @OMNI or any other mybb Guru's

[0xE9]

Ok so basically ALL my forums are mybb. There seems to now be a constant stream of spammers registering regardless of the captcha protection. They seem to spend quite some time on the registration page.

So what I'm wondering is there seem to be some sort of ajax script that when I unfocus the captcha textbox it tells me if I've typed the captcha correctly without having to actually post the page, thus if I get it wrong it tells me and doesn't generate a new image so I can try again.

Is it possible the spambots are using this to bruteforce the captcha without having to post the whole forum or is there some sort of limit with the amount of times the ajax script tells you it's wrong before you get a new captcha?