So far, we have focused on the classic XSS attack payload. It involves capturing a victim's session token, hijacking her session, and thereby making use of the application “as” the victim, performing arbitrary actions and potentially taking ownership of that user's account. In fact, numerous other attack payloads may be delivered via any type of XSS vulnerability.
This attack involves injecting malicious data into a page of a web application to feed misleading information to users of the application. It may simply involve injecting HTML markup into the site, or it may use scripts (sometimes hosted on an external server) to inject elaborate content and navigation into the site. This kind of attack is known as virtual defacement because the actual content hosted on the target's web server is not modified. The defacement is generated solely because of how the application processes and renders user-supplied input.
In addition to frivolous mischief, this kind of attack could be used for serious criminal purposes. A professionally crafted defacement, delivered to the right recipients in a convincing manner, could be picked up by the news media and have real-world effects on people's behavior, stock prices, and so on, to the attacker's financial benefit, as illustrated in Figure 12-6.