Clickjacking is a browser security issue and is a vulnerability across a variety of browsers and platforms. A clickjack takes the form of embedded code or a script that can execute without the user's knowledge, such as clicking on a button that appears to perform another function. The hacker installs an invisible layer over the existing site, hijacking the user's clicks. The suspicious-less user will perform this way actions they never intended to, from apparently inoffensive ones, as following someone on Twitter, to really nasty things, like password, credit card information theft, and anything else you might (not want to) do on a webpage.