XSS, Cross Site Scripting, CWE-79, CAPEC-86, bs.serving-sys.com

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Report generated by XSS.CX at Wed Mar 09 13:02:52 CST 2011.

The DORK Report

1. Cross-site scripting (reflected) next

Summary

Severity:	High
Confidence:	Certain
Host:	http://bs.serving-sys.com
Path:	/BurstingPipe/ActivityServer.bs

Issue detail

The value of the var request parameter is copied into a JavaScript expression which is not encapsulated in any quotation marks. The payload f523e%3balert(1)//df32b87a2b5 was submitted in the var parameter. This input was echoed as f523e;alert(1)//df32b87a2b5 in the application's response.

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

Remediation detail

Echoing user-controllable data within a script context is inherently dangerous and can make XSS attacks difficult to prevent. If at all possible, the application should avoid echoing user data within this context.

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 /BurstingPipe/ActivityServer.bs?cn=as&vn=omn&activityID=32638&advID=33048&var=s_1_Integrate_Eyeblaster_ACM_get_0f523e%3balert(1)//df32b87a2b5&rnd=9151038548447 HTTP/1.1
Host: bs.serving-sys.com
Proxy-Connection: keep-alive
Referer: http://www.rackspace.com/managed_hosting/services/proservices/sharepoint.php?CMP=Google_sharepoint_exact
Accept: */*
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
Cookie: C4=; u2=3a6c8499-0c84-46b7-b54f-f22315d657803GI08g; eyeblaster=BWVal=3746&BWDate=40608.545637&debuglevel=&FLV=10.2154&RES=128&WMPV=0; A3=hvPTaiJy0c6L00001gnesamti0cbS00001hK5Samaw0bfZ00001hgLkaoG50bMK00001hGiPaoG503sY00000hK5JalZa0bfZ00002hhb3aoGR0aVXaoGR1gEKaaoM009MT00000htGGaoFg0aQh00001hpHlaoI503sY00001gIlWai180aCf00001hRMoaoFg0bfg00005heSmakII0c9M00001gEJ.aoM209MT00000hUzhaoFh0ckv00001gCb0amtV08Y500001gnhgai180cbS00001gnfzamti0cbS00001; B3=8hkM0000000001ty8z6A0000000003tr7.VG0000000001ts86hj0000000001ts8r8g0000000001tf88kt0000000000ty8t7R0000000005ty8IWT0000000001ty88kE0000000000ty7.VO0000000001ts8z130000000001th8y030000000000ty8w1t0000000001ty8vdX0000000001ty8qaI0000000001tn7.Ws0000000001tf

Response

HTTP/1.1 200 OK
Cache-Control: no-cache, no-store
Pragma: no-cache
Content-Type: text/html
Expires: Sun, 05-Jun-2005 22:00:00 GMT
Vary: Accept-Encoding
P3P: CP="NOI DEVa OUR BUS UNI"
Date: Tue, 08 Mar 2011 20:53:22 GMT
Connection: close
Content-Length: 89

var s_1_Integrate_Eyeblaster_ACM_get_0f523e;alert(1)//df32b87a2b5 = {"errorCode": "nc" };

2. HTML does not specify charset previous next

Summary

Severity:	Information
Confidence:	Certain
Host:	http://bs.serving-sys.com
Path:	/BurstingPipe/ActivityServer.bs

Issue description

If a web response states that it contains HTML content but does not specify a character set, then the browser may analyse the HTML and attempt to determine which character set it appears to be using. Even if the majority of the HTML actually employs a standard character set such as UTF-8, the presence of non-standard characters anywhere in the response may cause the browser to interpret the content using a different character set. This can have unexpected results, and can lead to cross-site scripting vulnerabilities in which non-standard encodings like UTF-7 can be used to bypass the application's defensive filters.

In most cases, the absence of a charset directive does not constitute a security flaw, particularly if the response contains static content. You should review the contents of the response and the context in which it appears to determine whether any vulnerability exists.

Issue remediation

For every response containing HTML content, the application should include within the Content-type header a directive specifying a standard recognised character set, for example charset=ISO-8859-1.

Request

GET /BurstingPipe/ActivityServer.bs?cn=as&vn=omn&activityID=32638&advID=33048&var=s_1_Integrate_Eyeblaster_ACM_get_0&rnd=9151038548447 HTTP/1.1
Host: bs.serving-sys.com
Proxy-Connection: keep-alive
Referer: http://www.rackspace.com/managed_hosting/services/proservices/sharepoint.php?CMP=Google_sharepoint_exact
Accept: */*
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
Cookie: C4=; u2=3a6c8499-0c84-46b7-b54f-f22315d657803GI08g; eyeblaster=BWVal=3746&BWDate=40608.545637&debuglevel=&FLV=10.2154&RES=128&WMPV=0; A3=hvPTaiJy0c6L00001gnesamti0cbS00001hK5Samaw0bfZ00001hgLkaoG50bMK00001hGiPaoG503sY00000hK5JalZa0bfZ00002hhb3aoGR0aVXaoGR1gEKaaoM009MT00000htGGaoFg0aQh00001hpHlaoI503sY00001gIlWai180aCf00001hRMoaoFg0bfg00005heSmakII0c9M00001gEJ.aoM209MT00000hUzhaoFh0ckv00001gCb0amtV08Y500001gnhgai180cbS00001gnfzamti0cbS00001; B3=8hkM0000000001ty8z6A0000000003tr7.VG0000000001ts86hj0000000001ts8r8g0000000001tf88kt0000000000ty8t7R0000000005ty8IWT0000000001ty88kE0000000000ty7.VO0000000001ts8z130000000001th8y030000000000ty8w1t0000000001ty8vdX0000000001ty8qaI0000000001tn7.Ws0000000001tf

Response

HTTP/1.1 200 OK
Cache-Control: no-cache, no-store
Pragma: no-cache
Content-Type: text/html
Expires: Sun, 05-Jun-2005 22:00:00 GMT
Vary: Accept-Encoding
P3P: CP="NOI DEVa OUR BUS UNI"
Date: Tue, 08 Mar 2011 20:53:22 GMT
Connection: close
Content-Length: 62

var s_1_Integrate_Eyeblaster_ACM_get_0 = {"errorCode": "nc" };

3. Content type incorrectly stated previous

Summary

Severity:	Information
Confidence:	Firm
Host:	http://bs.serving-sys.com
Path:	/BurstingPipe/ActivityServer.bs

Issue detail

The response contains the following Content-type statement:

Content-Type: text/html

The response states that it contains HTML. However, it actually appears to contain script.

Issue background

If a web response specifies an incorrect content type, then browsers may process the response in unexpected ways. If the specified content type is a renderable text-based format, then the browser will usually attempt to parse and render the response in that format. If the specified type is an image format, then the browser will usually detect the anomaly and will analyse the actual content and attempt to determine its MIME type. Either case can lead to unexpected results, and if the content contains any user-controllable data may lead to cross-site scripting or other client-side vulnerabilities.

In most cases, the presence of an incorrect content type statement does not constitute a security flaw, particularly if the response contains static content. You should review the contents of the response and the context in which it appears to determine whether any vulnerability exists.

Issue remediation

For every response containing a message body, the application should include a single Content-type header which correctly and unambiguously states the MIME type of the content in the response body.

Request

Response

HTTP/1.1 200 OK
Cache-Control: no-cache, no-store
Pragma: no-cache
Content-Type: text/html
Expires: Sun, 05-Jun-2005 22:00:00 GMT
Vary: Accept-Encoding
P3P: CP="NOI DEVa OUR BUS UNI"
Date: Tue, 08 Mar 2011 20:53:22 GMT
Connection: close
Content-Length: 62

var s_1_Integrate_Eyeblaster_ACM_get_0 = {"errorCode": "nc" };

Report generated by XSS.CX at Wed Mar 09 13:02:52 CST 2011.