2. XML poisoning

XML traffic goes back and forth between server and browser in many of the WEB 2.0 applications. Web applications consume XML blocks coming from AJAX clients. It is possible to poison this XML block. Not uncommon is the technique to apply recursive payloads to similar-producing XML nodes multiple times. If the engine’s handling is poor this may result in a denial of services on the server. Many attackers also produce malformed XML documents that can disrupt logic depending on parsing mechanisms in use on the server. There are two types of parsing mechanisms available on the server side – SAX and DOM. This same attack vector is also used with Web services since they consume SOAP messages and SOAP messages are nothing but XML messages. Large-scale adaptation of XMLs at the application layer opens up new opportunities to use this new attack vector.

XML external entity reference is an XML property which can be manipulated by an attacker. This can lead to arbitrary file or TCP connection openings that can be leveraged by an attacker. XML schema poisoning is another XML poisoning attack vector which can change execution flow. This vulnerability can help an attacker to compromise confidential information.

3. Malicious AJAX code execution

AJAX calls are very silent and end-users would not be able to determine whether or not the browser is making silent calls using the XMLHTTPRequest object. When the browser makes an AJAX call to any Web site it replays cookies for each request. This can lead to potential opportunities for compromise. For example, John has logged in to his bank and authenticated on the server. After completing the authentication process he gets a session cookie. His bank’s page has a lot of critical information. Now he browses other pages while still logged in to his bank’s account Web page and lands at an attacker’s Web page. On this page the attacker has written silent AJAX code which makes backend calls to his bank without John’s consent, fetches critical information from the pages and sends this information to the attacker’s Web site. This leads to a security breach and leakage of confidential information.


4. RSS / Atom injection

This is a new WEB 2.0 attack. RSS feeds are common means of sharing information on portals and Web applications. These feeds are consumed by Web applications and sent to the browser on the client-side. One can inject literal JavaScripts into the RSS feeds to generate attacks on the client browser. An end user visits this particular Web site loads the page with the RSS feed and the malicious script – a script that can install software or steal cookies – gets executed. This is a lethal client-side attack. Worse, it can be mutated. With RSS and ATOM feeds becoming integral part of Web applications, it is important to filter out certain characters on the server-side before pushing the data out to the end user.

5. WSDL scanning and enumeration

WSDL (Web Services Definition Language) is an interface to Web services. This file provides key information about technologies, exposed methods, invocation patterns, etc. This is very sensitive information and can help in defining exploitation methods. Unnecessary functions or methods kept open can cause potential disaster for Web services. It is important to protect WSDL file or provide limited access to it. In real case scenarios, it is possible to discover several vulnerabilities using WSDL scanning.