the-web-application-hackers-handbook

Chapter 13 n Attacking Users: Other Techniques 541
visit a different URL than the one requested. These vulnerabilities usually are
of much less interest to an attacker than cross-site scripting, which can be used
to perform a much wider range of malicious actions. Open redirection bugs
are primarily of use in phishing attacks in which an attacker seeks to induce a
victim to visit a spoofed website and enter sensitive details. A redirection vulnerability
can lend credibility to the attacker’s overtures to potential victims,
because it enables him to construct a URL that points to the authentic website
he is targeting. Therefore, this URL is more convincing, and anyone who visits
it is redirected silently to a website that the attacker controls.
That said, the majority of real-world phishing-style attacks use other techniques
to gain credibility that are outside the control of the application being targeted.
Examples include registering similar domain names, using official-sounding subdomains,
and creating a simple mismatch between the anchor text and the target
URLs of links in HTML e-mails. Research has indicated that most users cannot
or are not inclined to make security decisions based on URL structure. For these
reasons, the value to phishermen of a typical open redirection bug is fairly marginal.
In recent years, open redirection vulnerabilities have been used in a relatively
benign way to perform “rickrolling” attacks, in which victims are unwittingly
redirected to a video of British pop legend Rick Astley, as illustrated in Figure 13-5.
Figure 13-5: The result of a rickrolling attack