Hai Nam Luke has discovered a vulnerability in Yahoo Messenger, which potentially can be exploited by malicious users to compromise a user's system.

Input passed to the "First Name", "Last Name", and "Nickname" fields in the "Contact Details" option is not properly sanitised when displaying status notification messages to the user in a chat box. This can e.g. be exploited to execute a limited amount of arbitrary script code in the Local Zone (My Computer) context by inputting specially crafted image tags in the aforementioned fields, tricking a target user into adding the attacker to the messenger list, sending a message to the target user, and then changing the status e.g. from "Available" to "Invisible To Everyone".

Successful exploitation requires that the attacker is in the messenger list of the target.

NOTE: When a user adds another user to the messenger list, the contact details get truncated, which limits the amount of script code that can be inserted.

The vulnerability is confirmed in version 8.1.0.209. Other versions may also be affected.

Solution
Add only trusted users to the messenger list.

Provided and/or discovered by
Hai Nam Luke

Changelog
Further details available to Secunia VIM customers

Original Advisory
http://archives.neohapsis.com/archives/bugtraq/2007-01/0613.html

Deep Links
Links available to Secunia VIM customers