Secunia Research has discovered a vulnerability in Thunderbird, which can be exploited by malicious people to trick users into executing arbitrary programs.

The vulnerability is caused due to attachments not being displayed correctly in mails. This can be exploited to spoof the file extension and the associated file type icon via a combination of overly long filenames containing whitespaces and "Content-Type" headers not matching the file extension.

Successful exploitation may lead to malware being saved to e.g. the desktop.

NOTE: Attachments can be saved by dragging the attachment, or using the "Save As..." or "Save All..." functionality. For files on the desktop, the icon can be spoofed if it e.g. is a ".exe" or ".lnk" file.

The vulnerability has been confirmed in versions 1.0.2, 1.0.6, and 1.0.7. Other versions may also be affected. Only the Microsoft Windows platform is affected.

Solution: Update to version 1.5
http://www.mozilla.com/thunderbird/

http://secunia.com/advisories/15907/