malerisch.net

Security advisory

CoolPreviews Chrome Privileged Code Injection

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|Description|
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Security-Assessment.com discovered that Coolpreviews stack feature is vulnerable to Cross Site Scripting
injection. The Coolpreviews stack previews link content within a Chrome window positioned on the right
side of the browser window. A malicious page is then able to pass arbitrary browser code, such as
JavaScript, via a link that points to a data URI which embeds the cross site scripting payload. The injected
browser code is rendered and executed in the chrome privileged Firefox zone.
The code is automatically executed when the user adds the malicious link to the stack (by default, right
click and then Cool Previews – Add To Stack).

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|Exploitation|
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This vulnerability can be exploited in several ways.
As the injection point is in the chrome privileged browser zone, it is possible to bypass Same Origin
Policy (SOP) protections, and also access Mozilla built-in XPCOM components. XPCOM components can be used to read and write from the file system, as well as execute arbitrary commands, steal stored passwords, or modify other Firefox extensions.

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|Solution|
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Security-Assessment.com follows responsible disclosure and promptly contacted the developer after discovering the issue. The developer was contacted on March 5, 2009, and no response was received. A fix was silently released on April 20, 2009.

Install the latest CoolPreviews version. This is available from Mozilla Add-ons website
(https://addons.mozilla.org/en-US/firefox/addon/2207).

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|Credit|
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Discovered and advised to the CoolPreviews vendor March 2009 by Roberto Suggi Liverani of Security-
Assessment.com. Personal Page: http://malerisch.net/

For full details regarding this vulnerability (including a detailed proof of concept exploit)
download the PDF from our website:
http://www.security-assessment.com/files/advisories/CoolPreviews_Firefox_Extension_Security_Advisory.pdf

For more details regarding exploitation of Firefox extensions, refer to our DEFCON 17 presentation at

http://www.security-assessment.com/files/presentations/liverani_freeman_abusing_firefox_extensions_defcon17.pdf

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