In this chapter, we looked at how XXE exploitation can be practical in an engagement. We then explored the potential DoS conditions that, when used with care, can provide distraction during a red-team attack.
We also examined XML-based request forgery attacks to not only perform a port scan but also chain exploits to reach vulnerable applications that we would otherwise not have access to. A more common use of XXE is to leak valuable information from the target application. We not only looked at the traditional exfiltration of data but also scenarios in which out-of-band communication was necessary. Using our cloud C2 server, we were able to exfiltrate data using a blind XXE attack.
Finally, we discovered how remote code execution can be achieved using XXE. While not as common, older application deployments may still fall victim to these types of exploits.
As shown throughout this chapter, file format parsers may seem benign, but with added features comes complexity, and complexity...