Unknown versions of Internet Explorer and Outlook allow remote attackers to spoof a legitimate URL in the status bar via A HREF tags with modified "alt" values that point to the legitimate site, combined with an image map whose href points to the malicious site, which facilitates a "phishing" attack.
Microsoft Outlook 8.5 and earlier, and Outlook Express 5 and earlier, with the "Automatically put people I reply to in my address book" option enabled, do not notify the user when the "Reply-To" address is different than the "From" address, which could allow an untrusted remote attacker to spoof legitimate addresses and intercept email from the client that is intended for another user.