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 attacker leverages this capability to execute scripts to execute his/her own script by embedding it within other scripts that the target software is likely to execute. The attacker must have the ability to inject script into script that is likely to be executed. If this is done, then the attacker 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. Of course, 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. In general all that is required is for there to be sufficient privileges to execute a script, but not protected against writing.
Prerequisites Target software must be able to execute scripts, and also allow attacker to write/upload script
Solutions Design: Use browser technologies that do not allow client side scripting. Design: Utilize strict type, character, and encoding enforcement Design: 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. Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification. Implementation: Perform input validation for all remote content. Implementation: Perform output validation for all remote content. Implementation: Disable scripting languages such as JavaScript in browser Implementation: Session tokens for specific host Implementation: 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. Implementation: 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-71 Apple '.DS_Store'
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-276 Incorrect Default Permissions
CWE-279 Incorrect Execution-Assigned Permissions
CWE-284 Improper Access Control
CWE-692
CWE-697 Insufficient Comparison
CWE-713
Back to Top