Simon Willison’s Weblog

“Likejacking” Takes Off on Facebook. The Facebook Like button is vulnerable to Clickjacking, and is being widely exploited. Since Likes show up in your Facebook stream, it’s an easy attack to make viral. The button is implemented on third party sites as an iframe, which would seem to me to be exploitable by design (just make the iframe transparent in the parent document and trick the user in to clicking in the right place). I can’t think of any way they could support the embedded Like button without being vulnerable to clickjacking, since clickjacking prevention relies on not allowing your UI elements to be embedded in a hostile site while the Like button’s functionality depends on exactly that. # 3rd June 2010, 10:01 am

Busting frame busting: a study of clickjacking vulnerabilities at popular sites (via) Fascinating and highly readable security paper from the Stanford Web Security Research group. Clickjacking can be mitigated using framebusting techniques, but it turns out that almost all of those techniques can be broken in various ways. Fun examples include double-nesting iframes so that the framebusting script overwrites the top-level frame rather than the whole window, and a devious attack against the IE and Chrome XSS filters which tricks them in to deleting the framebusting JavaScript by reflecting portions of it in the framed page’s URL. The authors suggest a new framebusting snippet that should be more effective, but sadly it relies on blanking out the whole page in CSS and making it visible again in JavaScript, making it inaccessible to browsers with JavaScript disabled. # 24th May 2010, 11:40 am

Why an OAuth iframe is a Great Idea. Because users should a) learn to be phished and b) not even be given the option to avoid being phished if they know what they’re doing? No, no and thrice no. If you want to improve the experience, use a popup window so the user can still see the site they are signing in to in the background. # 16th July 2009, 8:29 pm

Ehy IE8, I Can Has Some Clickjacking Protection? (via) IE8 has built-in protection against clickjacking, but it’s opt-in (with a custom HTTP header) and IE only. It turns out the usual defence against clickjacking (using framebusting JavaScript) doesn’t work in IE as it can be worked around with a security=“restricted” attribute on an iframe. # 29th January 2009, 1:39 pm

FB App Canvas Pages: I Think I’d Use IFrames. Facebook’s Charlie Cheever explains the difference between FBML canvas pages, iframe pages and XFBML when building Facebook apps. I’m always surprised at APIs that load untrusted content in an iframe, as it seems like an invitation for frame-busting phishing attacks. # 2nd October 2008, 2:39 pm

This Week in HTML 5—Episode 7: Clickjacking. Clickjacking is when a third party site is embedded in an iframe with opacity 0 and positioned such that a click on the page actually hits a button on the now invisible third party site. Mark Pilgrim explains how the NoScript site uses this in a non malicious way to for the “install now!” button. # 1st October 2008, 1:48 am

Firefox promiscuous IFRAME access bug. Lets malicious sites “display disruptive or misleading contents in the context of an attacked site” and intercept keystrokes! The demo worked in Camino 1.5 as well. Avoid using Gecko-based browsers until this is patched? # 6th June 2007, 10 am