Over the weekend at the New England Code Camp 7 conference, I mentioned briefly about some of the potential security problems with AJAX. Dana Epp has a post about the new class of attack vectors using Javascript Hijacking against AJAX, and ultimately, ATLAS, applications. He points to a research paper by Fortify Software that details the vulnerabilities, how the attacks could be performed, and ways to mitigate against them.
Be sure to read Dana's post and read the research paper. Consider Dana's post and warning to make mitigating against this type of threat as part of your own company's threat model process.