You don't need any plugin. Turn your scripts on.
I have scripts enabled for kraken.com in FF but still can't see the monster. IE shows the monster however.
Just refresh until it gives you something readable.
Thanks
Firefox simply doesn't play nice with our site at the present time - IE or Chrome are recommended instead. We are working on a fix for Firefox, but there are multiple issues, some of which seem to depend on OS. Firefox is high priority for us, but our front end developer also has many other high priority projects to manage at the moment, so we don't have an ETA on this.
Just to clarify in case some didn't understand, if you can't read the captcha, just click the "refresh" icon until you get something you can read.