An elevation of privilege vulnerability exists when Microsoft Outlook does not validate attachment headers properly. An attacker who successfully exploited the vulnerability could send an email with hidden attachments that would be opened or executed once a victim clicks a link within the email. Note that this does not bypass attachment filters, so blocked attachments will still be excluded. To exploit the vulnerability, the attacker could send a specially crafted email to a victim. The victim would then be required to click on a link within the email to open or execute a malicious attachment. This update addresses the vulnerability by changing the way that Outlook parses attachment headers.