CAPEC-32

Detailed Abstraction Level
Meta — Very abstract, high-level category
Standard — Specific enough to understand
Detailed — Tied to specific technique Draft MITRE CAPEC Status
Stable — Fully reviewed and complete
Draft — Under development
Incomplete — Partially defined
Deprecated — No longer recommended
Obsolete — Replaced by another CAPEC Likelihood: High Severity: High
XSS Through HTTP Query Strings

Description

An adversary embeds malicious script code in the parameters of an HTTP query string and convinces a victim to submit the HTTP request that contains the query string to a vulnerable web application. The web application then procedes to use the values parameters without properly validation them first and generates the HTML code that will be executed by the victim's browser.

Prerequisites

Target client software must allow scripting such as JavaScript. Server software must allow display of remote generated HTML without sufficient input or output validation.

Mitigations

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, including remote and user-generated 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

Skills Required

[Low] To place malicious payload on server via HTTP

[High] Exploiting any information gathered by HTTP Query on script host