Web sites use cookies as a way to store information on a user's local system. Most often, this information is used for customizing and retaining a site's setting for a user across multiple sessions. By design each site should maintain its own cookies on a user's machine and be able to access only those cookies.
A vulnerability exists because it is possible to craft a URL that can allow sites to gain unauthorized access to user's cookies and potentially modify the values contained in them. Because some web sites store sensitive information in a user's cookies, it is also possible that personal information could be exposed.
Microsoft is preparing a patch for this issue, but in the meantime customers can protect their systems by disabling active scripting. (The FAQ provides step-by-step instructions for doing this). This will protect against both the web-hosted and the mail-borne variants discussed above. When the patch is complete, Microsoft will re-release this bulletin and provide details on obtaining and using it.
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