Researchers have discovered that inadequate security restrictions in Internet Explorer make it possible for an attacker to execute script on any Web page that containing frames.
Grey Magic Software describes the vulnerability as critical, a warning backed up by several proof of concept demonstrations.
Because of the way frames (and iframes) are handled by IE version 5.5 and above, attackers are able to get to all sorts of mischief with minimal effort, including:
- Read local files from the victim's hard drive, using a default local resource (ironically dubbed "PrivacyPolicy") that contains frames in IE
- Execute arbitrary programs on the victim's computer, using the woefully misnamed "PrivacyPolicy" resource
- Read a victim's cookie and content from any remote site that contains a frame, which can lead to session-stealing and account compromise on sites containing frames - such as Hotmail
- Forge the content of any site that contains a frame. For example, the attacker could show the user a fake login screen at hotmail.com and log the results to a database
Users of Internet Explorer 5.5 and above are vulnerable to these various exploits with IE 6.0 users particularly vulnerable.
Fortunately there is a simple workaround available which involves disabling Active Scripting. Well either that or consider moving to an alternative browser.
GreyMagic published its advisory yesterday after discovering the flaw in August 4. Still no word from Microsoft on the issue, a fix for this particular problem doesn't appear in a list of fixes included in Microsoft's release of Service Pack 1 for IE6, which was released today. ®