Attack of the CSRF

Cross-Site Request Forgery (also referred to as Cross-Site Reference Forgery, CSRF and XSRF) is  apidly becoming a serious security problem of which most programmers and users are blissfully unaware. CSRF is a web-based attack that has grown out of, and remains a close cousin to, the more traditional Cross-Site Scripting (XSS) attacks. In an XSS exploit, the attacker inputs malicious content into a web application (e.g., by creating a malformed URL or embedding hostile code in a response box) that results in hostile content such as JavaScript being inserted into otherwise safe content that then is served to the victim. CSRF attacks take it a step further by inserting hostile content that results in an action by the user's web browser, such as changing a filter setting within web-based email or initiating a money transfer from an online bank account.

A CSRF Attack Example

So you go to your favorite social networking site to chat with friends. Unfortunately, the site in question allows users to insert images into web-based conversations (e.g., avatars for a forum). Instead of using a URL such as:

<img src="http://random-site/ image.jpg">

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