Next-Generation Clickjacking Attacks Revealed

Tomorrow at Black Hat Europe a researcher will demonstrate a new, powerful breed of clickjacking attacks he devised that can bypass newly constructed defenses in browsers and Websites.

Paul Stone, a security consultant with Context Information Security in the U.K., also will release a browser-based point-and-shoot tool for clickjacking that simplifies these attacks on Web applications and provides researchers visual views of the links, buttons, fields, and data to be targeted by the clickjacking attack.

Clickjacking is where an attacker slips a malicious link invisibly on a Web page or under a button on the site. When the user clicks on the link or moves his mouse over it, he becomes infected. Security researchers Robert "RSnake" Hansen and Jeremiah Grossman two years ago first exposed some of the dangers of clickjacking, and browser vendors like Microsoft have responded to the threat with anti-clickjacking defenses: Internet Explorer 8, for instance, contains a feature that lets Websites safeguard their sites from the attacks with an HTTP header that attaches to the Web pages.

"Clickjacking was first announced two years ago, but most sites aren't protected against it," Stone says. "And people don't realize how it works."

Facebook and Twitter both have suffered from clickjacking -- in December, Facebook was hit with an attack that came in the form of a comment on a user's account with a photo and a link. The link took the victim to a Web page that presented like a CAPTCHA or Turing test, and lured the user into clicking on the blue "Share" button on the Facebook page. A Web developer, meanwhile, released a proof-of-concept attack against Twitter that allowed an attacker to hijack a member's "update" function.

To date, clickjacking alone has been considered a fairly limited attack except when it's paired with cross-site scripting (XSS) and cross-site request forgery (CSRF) attacks.

"I've been looking at ways to inject data into a form, for say, online shopping or Webmail, using clickjacking and injecting data into the site without CSRF," Stone says.

He will demonstrate four new clickjacking techniques -- text-field injection, which could be used to target Webmail and document editors; content-extraction, which could be used for intranet reconnaissance; another form of text injection; and an iFrame attack that can be used to do things like determine whether a victim is logged into a particular site, such as Gmail, for example, so the attacker can target an attack there. These new clickjacking attacks can be used with the newest versions of IE, Firefox, Safari, and Chrome.

"Clickjacking has been mostly seen as a single click" attack, Stone says. "But with [one] new technique, you can just by clicking on something fill in fields of a form on online shopping or email or banking, and then click the 'submit' button to submit that data."

Stone, who wouldn't disclose details of the "tricks" behind his next-generation clickjacking attacks before his talk at Black Hat tomorrow, says he also found a way to steal information from Websites that aren't vulnerable to XSS or CSRF. "And I'm not using actual vulnerabilities in browsers: I'm just using the way they work against them," he says.

He says he will demonstrate how existing defenses against CSRF and clickjacking are breakable. "I will show tomorrow some of the techniques currently used to protect aren't all that effective -- some browser vulnerabilities are able to bypass these protections," he says.

"And I'll be showing...that existing mitigations can't protect" against these new clickjacking attacks, he says. That's because JavaScript-based protections like those used by IE and Firefox aren't effective, for instance, he says.

Stone's clickjacking tool, meanwhile, is aimed at showing researchers and Website owners how easy clickjacking attacks are to execute, and to encourage them to add protections against them, he says. The tool runs in the browser, and creates clickjacking attacks "in a visual way" so that the hidden elements are visible, he says.

"If you're trying to target a 'submit' button [on a Web page], you have to know how many pixels" it has on the page, for instance. "This tool lets you load up a page, select areas you want to target, and replay" the steps in the attack, he says.

The free Clickjacking Tool will be available from Context Information Security's Website tomorrow.

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