With HTML 5 the current web development moves from server side generated content and layout to client side generated. Most of the so called HTML5 powered websites use JavaScript and CSS for generating beautiful looking and responsive user experiences. This ultimately leads to the point were developers want to include or request third-party resources. Unfortunately all current browsers prevent scripts to request external resources through a security feature called the Same-Origin-Policy. This policy specifies that client side code could only request resources from the domain being executed from. This means that a script from example.com can not load a resource from google.com via AJAX(XHR/XmlHttpRequest).
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Cross-Site Request Forgery with Cross-Origin Resource Sharing
During one of our last projects in a large environment we encountered an interesting flaw. Although it was not possible to exploit it in this particular context, it’s worth to be mentioned here. The finding was about Cross-Site Request Forgery, a quite well-known attack that forces a user to execute unintended actions within the authenticated context of a web application. With a little help of social engineering (like sending a link via email, chat, embedded code in documents, etc…) an attacker may force the user to execute actions of the attacker’s choice.
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