An attacker can run arbitrary commands on Windows machines with a simple bit of HTML, an Israeli security researcher has demonstrated. The exploit will work with IE, Outlook and OutlooK Express even if active scripting and ActiveX are disabled in the browser security settings.
The problem here is data binding, an old 'feature' going back to IE4 in which a data source object (DSO) is bound to HTML.
Using an XML data source, the researchers operating a Web site called GreyMagic Software came up with a simple example in which a few lines will cause Windows to launch the calculator application thus:
<span datasrc="#oExec" datafld="exploit" dataformatas="html"></span>
<object id="oFile" classid="clsid:11111111-1111-1111-1111-111111111111" codebase="c:/windows/system32/calc.exe"></object>
You can copy and paste this into a text editor, though you must edit the path to calc.exe in the script if it differs from the path on your system, and name it whatever.htm. Then open the file with your browser and watch the calculator launch.
MS has yet to patch the hole, but we've verified that a workaround proposed by Axel Pettinger and Garland Hopkins works on the above example, though that's no guarantee that it will work on every exploit of this sort.
Using regedit.exe find the following key:
and change the value of "1004" (DWORD) from "0" to "3".
Don't forget to back up your registry before making changes, even innocuous ones like this.
You can then re-boot and open the example file with your browser again to verify that it fails to launch the calculator. However, the workaround will often cause IE to launch a security warning dialog box which has to be cleared before you can continue surfing. It tells you that your security settings are interfering with your rich Internet experience, and you can't tick a box ordering it to stop warning you of what you already know.
Personally I believe MS does this to discourage high security settings in IE which interfere with the rich eXPeriences advertisers have in store for you on the Web, and which MS seems inexplicably eager to vouchsafe. You don't get sick of the slightly scaled-down functionality; you get sick of the endless warnings and eventually capitulate and restore your settings to Redmond-approved, and Direct Marketing Association-approved, levels.
But we digress.
Obviously, there's a slew of malicious activities which can be attempted with this exploit, and a slew of people busily working on them. Thus it might be prudent to apply the workaround until Redmond issues a patch -- if you can stand to be harangued about your security settings at every turn, that is. ®