Secunia Research has discovered a vulnerability in Yahoo! Messenger, which can be exploited by malicious, local users to gain escalated privileges.

The vulnerability is caused due to a combination of weak default directory permissions and the Audio Setup Wizard (asw.dll) invoking the "ping.exe" utility insecurely during the connection testing phase. This can be exploited to execute arbitrary code with the privileges of another user by placing a malicious "ping.exe" file in the application's "Messenger" directory.

Successful exploitation requires that a user runs the Audio Setup Wizard and that the application has been installed in a non-default location (not as a subdirectory to the "Program Files" directory).

The vulnerability has been confirmed in version 6.0.0.1750 for Windows. Other versions may also be affected.

Solution:
Update to version 6.0.0.1921 or later.
http://messenger.yahoo.com/

Provided and/or discovered by:
Carsten Eiram, Secunia Research.

This one too...