Name Embedding Scripts within Scripts
Summary An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute scripts. The adversary leverages this capability to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The adversary must have the ability to inject their script into a script that is likely to be executed. If this is done, then the adversary can potentially launch a variety of probes and attacks against the web server's local environment, in many cases the so-called DMZ, back end resources the web server can communicate with, and other hosts. With the proliferation of intermediaries, such as Web App Firewalls, network devices, and even printers having JVMs and Web servers, there are many locales where an attacker can inject malicious scripts. Since this attack pattern defines scripts within scripts, there are likely privileges to execute said attack on the host. These attacks are not solely limited to the server side, client side scripts like Ajax and client side JavaScript can contain malicious scripts as well.
Prerequisites Target software must be able to execute scripts, and also grant the adversary privilege to write/upload scripts.
Solutions Use browser technologies that do not allow client side scripting. Utilize strict type, character, and encoding enforcement. Server side developers should not proxy content via XHR or other means. If a HTTP proxy for remote content is setup on the server side, the client's browser has no way of discerning where the data is originating from. Ensure all content that is delivered to client is sanitized against an acceptable content specification. Perform input validation for all remote content. Perform output validation for all remote content. Disable scripting languages such as JavaScript in browser Session tokens for specific host Patching software. There are many attack vectors for XSS on the client side and the server side. Many vulnerabilities are fixed in service packs for browser, web servers, and plug in technologies, staying current on patch release that deal with XSS countermeasures mitigates this. Privileges are constrained, if a script is loaded, ensure system runs in chroot jail or other limited authority mode
Related Weaknesses
CWE ID Description
CWE-284 Improper Access Control
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