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Clickjacking (was: window.open() and popup blockers)

From: Anssi Kostiainen <anssi.kostiainen@nokia.com>
Date: Wed, 6 Oct 2010 20:38:04 +0300
Cc: "Oksanen Ilkka (Nokia-MS/Espoo)" <Ilkka.Oksanen@nokia.com>, "public-device-apis@w3.org WG" <public-device-apis@w3.org>, "Hirsch Frederick (Nokia-CIC/Boston)" <Frederick.Hirsch@nokia.com>
Message-Id: <D131C76E-1631-43D7-9384-73EDA1E93B0E@nokia.com>
To: ext Rich Tibbett <richt@opera.com>
Hi,

On 4.10.2010, at 13.57, ext Rich Tibbett wrote:

> I have added a section to the Contacts API spec entitled 'API Invocation 
> via DOM Events' + an example of its usage. It is included informatively 
> and might be worth a read:
> 
> http://dev.w3.org/2009/dap/contacts/Overview.html#api-invocation-via-dom-events

Thanks. A concrete proposal is a good way to start mulling this one. Before going full steam ahead with the approach I'd like to make sure we won't increase the attack surface too much.

Some of us surely remember e.g. the Flash webcam clickjacking exploit [3]. I'd guess a similarly constructed attack could be used to trick the user in displaying a contact picker, from where the confused user could proceed to share his/her contact information with a malicious party. In Capture constructing a similar attack would be even easier due to simpler file picker interaction. AFAIK this type of an attack does not work with an asynchronous infobar which is outside of the viewport and not within the top-level browsing context, and thus is not accessible by script.

Below are couple of good references on clickjacking I found:

- Clickjacking article by the Open Web Application Security Project, OWASP [1]

- Busting Frame Busting: a Study of Clickjacking Vulnerabilities on Popular Sites by the Stanford Web Security group [2] (cited by the OWASP article)

- Clickjacking exploit explained by Jeremiah Grossman and Robert Hansen, who coined the term clickjacking (describes the original Flash webcam exploit) [3]

I looked into public-web-security ML but found very little discussion on clickjacking. Basically there was a one thread regarding HTML5 iframe sandboxing concluding X-Frame-Options HTTP header would be the solution [4]. The Stanford paper [2] seem to also conclude X-Frame-Options is the long-term solution. This Week in HTML5 also discusses potential workarounds [5].

I guess we could benefit from a review by web security experts at this early stage of the design. What would be the best venue to conduct that?

-Anssi

[1] http://www.owasp.org/index.php/Clickjacking 
[2] http://w2spconf.com/2010/papers/p27.pdf
[3] http://www.sectheory.com/clickjacking.htm
[4] http://lists.w3.org/Archives/Public/public-web-security/2009Dec/0132.html
[5] http://blog.whatwg.org/this-week-in-html-5-episode-7
Received on Wednesday, 6 October 2010 17:39:34 UTC

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