Serious XSS Vulnerability in RapidShare
Researchers from M86 Security have found a serious cross site scripting (XSS) vulnerability in the RapidShare.com website. This XSS allowes attackers to scam users. Rapidshare is one of the top 50 website and used for file hosting. Many hackers use this to host malwares and copyright materials.
This is a DOM-based cross-site scripting attack that relies on the victim opening a specially crafted URL and is invisible to the server because the malicious link contains the # fragmenting character before the payload.
Attackers could send fake emails with a link to an allegedly interesting file, for example, something like "WikiLeaks releases video of American soldiers shooting innocent civilians in Iraq. Download here: http://rapidshare.com/files/[file_id]/[file_name].avi"
In reality, the link would point to a specially crafted rapidshare.com URL which, when opened in the browser, would display an error page with a message reading: "Too many users downloading from the server right now. Get a 80% discount coupon for a Pro Account by sending a free SMS to [premium rate number]. Limited offer."
In this case, people interested in getting a Pro account for a low price would send what they believe to be a free SMS - but which actually isn't - to a special number set up by the scammer.
Fortunately, this vulnerability was not found by cybercriminals, but by researchers who responsibly reported it to RapidShare. The issue has since been resolved, but the incident serves as a good example of how a simple input validation flaw on a popular website can be exploited for financial gain.