I had earlier written about my attempts to break into OpenSocial on Orkut. The hack basically exploited script injection into an application called emote. The hack has since been fixed, but I thought it would make sense to write about the potential problems that such hacks in application can have.
The applications open in iFrames from a different source and hence, script injection cannot really steal orkut cookies. However, since they definitely are embedded in the page, people could exploit it for phishing Google accounts. All that the iFrame is required to do is call a kill frames script and redirect the user to an account page resembling the Orkut login page. If the user is tricked into believing that Orkut did indeed log him out, credentials may be entered, making the phisher collect "GOOGLE CREDENTIALS". These could in turn be used to log into gmail, docs, etc.
Another possible attack is that of a cross site request forgery. Many other opensocial application are not guarded against this. Inserting an iFrame would be a classic way to sent request to those other applications for tasks that a user may never intend. This could typically include placing a bet on a wrong team in those betting applications to deleting books from a bookshelf application. I am currently working on demonstrating this hack and need to find an injection in some other application to make requests. Watch this space for updates.