Outlook Express is prone to a cross-domain information-disclosure vulnerability. This vulnerability may let a malicious website access properties of a site in an arbitrary external domain in the context of the victim's browser. Attackers could exploit this issue to access sensitive information (such as cookies or passwords) that is associated with the external domain.
Run all software as a nonprivileged user with minimal access rights.
Ensure that all nonadministrative tasks, such as browsing the web and reading email, are performed as an unprivileged user with minimal access rights.
Do not follow links provided by unknown or untrusted sources.
Users should never visit sites of questionable integrity or follow links provided by unfamiliar or untrusted sources.
Set web browser security to disable the execution of script code or active content.
To limit exposure to this and other vulnerabilities, disable scripting and active content in the Internet Zone.
Disable any services that are not needed.
To limit email-based attack vectors for this and other vulnerabilities, disable support for HTML email in the email client.
The vendor has released an advisory to address this issue in supported applications. Please see the referenced advisory for details on obtaining the appropriate updates.