Original URL: http://www.theregister.co.uk/2009/11/13/adobe_flash_wallop/

Adobe Flash attack vector exploits insecure web design

User-supplied malware upload peril

By John Leyden

Posted in Security, 13th November 2009 15:32 GMT

An unpatched security risk involving Adobe Flash creates a possible mechanism for hackers to load exploits onto websites.

The vulnerability was discovered by security researchers at Foreground Security and reported to both Adobe and Google, whose Google Applications, including Gmail, are potentially vulnerable to exploit.

No fix is currently available. However, exploitation of the security flaw would be far from straightforward, especially on Gmail because hackers would have to figure out message IDs in order to create any mischief. Foreground has not detected any attacks using the technique, which affects sites that allow users to upload active content onto trusted domains.

Proof of concept demos on the vulnerability created by Foreground revolve around the misuse of Adobe Flash to potentially booby-trap targeted websites with drive-by download exploits. One (now fixed) Gmail Exploit that revolves around the misuse of Adobe Flash can be found below.

The threat is far from restricted to Adobe Flash and could involve other forms of active content, including JavaScript. The root cause of the problem arguably lies with insecure web design practices that are deeply ingrained on the internet.

Brad Arkin, Adobe's director for product security and privacy, explained that simply patching Flash won't solve the problem. "We see this as a generic problem that affects any site that allows active scripting, not just Flash, but things like JavaScript and Silverlight as well," Arkin told Computerworld. "Sites should not allow user uploads to a trusted domain."

Mike Bailey, the senior researcher who first documented the vulnerability, agreed with that point while adding that Adobe also has a role to play in fixing the problem.

"For website owners, all user-supplied content should be served from a completely separate domain,” Bailey said. "This is already implemented by Yahoo mail, Hotmail, Wikipedia, and many other major websites, but a huge variety of self-contained web applications do not do so."

"The ideal fix should involve Adobe implementing a more sensible origin policy for Flash objects," Bailey added. However, the downside of making Flash more secure in this way is that it would break legitimate (though arguably badly coded) functionality on many sites.

Surfers are advised to mitigate against the possible risk of attack by disabling Flash in their browsers or by using browser plug-ins, such as NoScript for Firefox or ToggleFlash for IE, to reduce their exposure whenever possible.

More detail on the vulnerability can be found in Foreground Security advisory here. ®