Re: Cross-site Scripting with Local Privilege Vulnerability in Yahoo Messenger

Hi friends,

Bingo! It works on the Y!messenger version and have verified
it on my setup.
Quite strange indeed! Good finding ;) Let us see if it can be "really"


On 1/28/07, Ahmed Sheipani <sheipani@xxxxxxxxx> wrote:
I have just tested this with Yahoo! Messenger , and it does not
seem to work..

However, I noticed that after setting the FirstName parameter to a very long
one, the automatic notification message does not appear anymore.

-----Original Message-----
From: hainamluke@xxxxxxxxx [mailto:hainamluke@xxxxxxxxx]
Sent: Friday, January 26, 2007 7:27 AM
To: bugtraq@xxxxxxxxxxxxxxxxx
Subject: Cross-site Scripting with Local Privilege Vulnerability in Yahoo
Importance: High

I've found a cross-site scripting vulnerability in Yahoo! Messenger, a
popular advertisement-supported instant messaging client and protocol
provided by Yahoo! Attacker can inject a malicious script with local
privilege to Y!M notification message.

The vulnerability is discovered in the chat dialog. The automatic
notification message of Yahoo! Messenger, for instance "Hai Nam Luke has
signed out. (1/26/2007 10:03 PM)" or "Hai Nam Luke has signed back in.
(1/26/2007 10:04 PM)" can be easily exploited with injecting a malicious
script to. Script is disabled in chat messages but system notification
messasage. That Yahoo Messenger uses Internet Explorer to display messages,
the malicious script will be run with local privilege in the Internet
Explorer Temporary Folder. This serious vulnerability could allow attacker
gain the victim's system access.

Inject unexpected script also causes other Yahoo! Messenger's errors.

Yahoo! Messenger and previous versions

+ Firstname: Hai Nam Luke Hai Nam Luke Hai Nam Luke Hai Nam Luke . ( as long
as victim cant see the lastname)
+ Lastname: <img src="javascript:alert('Executed from ' +
top.location)" >
+ Request to add victim ID to your contact list.
+ Once victim accepts your request, send him a message and change your
online status (Available -> Invisible)

This vulnerability was reported to Yahoo!

Hai Nam Luke <hainamluke@xxxxxxxxx>
K46A - NEU

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