A few weeks ago, I announced my plan to post a series of FAXX (Facebook Application XSS+XSRF) hacks. In the spirit of previous series of vulnerability disclosures, I elected to post a new hole every day for the month of September. The effort quickly became known as the Month of Facebook Bugs, and today marks the halfway point.
Thus far, counting the “Make a Gift!” vulnerability as affecting one application, I’ve reported on 19 vulnerable applications, and all but one are patched. Of those 19 applications, 12 are Facebook Verified Applications, and 13 are capable of clickjacking installs. All types of applications have appeared in the series so far, with several coming from the top 10 by monthly active users. Ignoring any overlap and simply totaling all of the monthly active user figures from the 19 reports, the tally of vulnerable users would stand at just over 169 million. However, an application vulnerability affects any user who has ever authorized the application, regardless of how often they use it. Furthermore, a user who has not authorized an application is still susceptible to a clickjacking install.
The primary purposes of this series is to raise awareness – and with several audiences. First, many Facebook users apply the same level of trust to Facebook applications that they give to Facebook itself, and are completely unaware of application-based attacks or the prevalence of application vulnerabilities. Second, many application developers are overlooking basic security practices for web applications. Third, the technology community has not always seemed to realize the magnitude of issues present in the Facebook Platform today.
In fact, while I may ensure that 30 applications get patched, if a 31st remains vulnerable, users remain vulnerable. I’ve outlined before some of the problem I see in the architecture of the Platform, and I’ve sent those concerns to Facebook in communicating with them about these application holes. I’ve not received a response thus far, and honestly don’t expect one, but I do hope this month-long series helps illustrate more vividly why I’ve raised such concerns.
As of today, I have uncovered enough FAXX hacks to last through the rest of September. I’ve already made an effort to contact every developer affected to give them time for patches. Once the month ends, I plan on releasing source code that demonstrates how a FAXX hack can be exploited to steal profile information and launch viral attacks. In the mean time, thanks to everyone for help and feedback – and please keep spreading the word.