AOL's AIM is one of the most used IM clients in the world. According to Neilsen/Netratings, AOL had around 53 million IM subscribers in 2006.
A week ago, I've found a critical vulnerability in the latest version of AIM, which could allow an attacker to execute code from remote by simply sending a message to the victim.
Just before reporting the vulnerability to AOL, I've encountered a blog post by Ryan Naraine which describes a vulnerability in AIM that was found by "Shell". After reading the advisory, I understood that this vulnerability is a bit different from the one that I found, as it is in the Notification window which pops-up only when you are not in the middle of conversation with the attacker.
So, I've decided to report the vulnerability to AOL, and provided full description and Proof-of-Concepts. I have yet to receive any response from AOL.
Today, Core Labs have published an advisory which describes the general case of my findings. In the advisory they also claim that AOL has patched the vulnerability, so the latest beta version (v220.127.116.11) of AIM is not vulnerable anymore.
I've tested the PoC which I provided to AOL against the "patched" version. While the latest beta version seems to filter my PoC, I've been able to change my code a little and successfully exploited the vulnerability again.
The problem with AOL's patch is that they filter specific tags and attributes, instead of fixing the main cause of the vulnerability, which is locking down the local zone of their client's web-browser control.
Core Labs describes a workaround in their advisory which messes up with the registry. I think that the common people should avoid this workaround, and stop using AIM until a real fix from AOL will arrive.
I also encourage AOL security staff to contact me as soon as possible. I am willing to provide them with all the new information. I will not contact AOL again, as I'm still waiting for AOL to respond my first email.
[UPDATE:] I've just got an email from AOL which confirms that the "patched" beta version is still vulnerable:
We apologize, for not initially responding to your email. We have already fixed out client on these issues and the client is scheduled for a mid-October release. This fix is not yet in the current AIM beta client.
AOL Product Vulnerability Team
Again, try to avoid using AIM at-least until the mid-October release.