Cross Site Scripting Reports | Hoyt LLC Research

1. Cross-site scripting (reflected) next

Summary

Severity:	High
Confidence:	Certain
Host:	http://wd.sharethis.com
Path:	/api/getApi.php

Issue detail

The value of the cb request parameter is copied into the HTML document as plain text between tags. The payload 86a5d<script>alert(1)</script>521b186b286 was submitted in the cb parameter. This input was echoed unmodified in the application's response.

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

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.

Issue remediation

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 /api/getApi.php?return=json&url=http%3A%2F%2Fwww.pfizer.com%2Fabout%2F&fpc=7639673-12c56ffa879-2f6d2c61-12&cb=initWidgetOnSuccess86a5d<script>alert(1)</script>521b186b286&service=initWidget HTTP/1.1
Accept: */*
Referer: http://edge.sharethis.com/share4x/index.7dbd8c2c4a2160efef50761a91021817.html
Accept-Language: en-US
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)
Accept-Encoding: gzip, deflate
Host: wd.sharethis.com
Proxy-Connection: Keep-Alive
Cookie: __stid=CspST0zY2orBcjqxx2EuAg==

Response

HTTP/1.1 200 OK
Date: Tue, 16 Nov 2010 23:27:20 GMT
Server: Apache/2.2.14 (Ubuntu)
X-Powered-By: PHP/5.3.2-1ubuntu4.5
Vary: Accept-Encoding
Connection: close
Content-Type: text/html
Content-Length: 173

initWidgetOnSuccess86a5d<script>alert(1)</script>521b186b286({"status":"SUCCESS","data":{"session_token":"72084577c343161489faca942a684838","require_captcha":1,"ga":true}});

2. Session token in URL previous next

Summary

Severity:	Medium
Confidence:	Firm
Host:	http://wd.sharethis.com
Path:	/api/sharer.php

Issue detail

The URL in the request appears to contain a session token within the query string:

http://wd.sharethis.com/api/sharer.php?destination=digg&url=http%3A%2F%2Fwww.pfizer.com%2Fabout%2F&title=About%20Pfizer%20%7C%20Pfizer%3A%20the%20world's%20largest%20research-based%20pharmaceutical%20company&publisher=f5782661-29c9-43d9-81d8-7bdce05b3a3b&fpc=7639673-12c56ffa879-2f6d2c61-12&sessionID=1289949989299.31735&source=chicklet

Issue background

Sensitive information within URLs may be logged in various locations, including the user's browser, the web server, and any forward or reverse proxy servers between the two endpoints. URLs may also be displayed on-screen, bookmarked or emailed around by users. They may be disclosed to third parties via the Referer header when any off-site links are followed. Placing session tokens into the URL increases the risk that they will be captured by an attacker.

Issue remediation

The application should use an alternative mechanism for transmitting session tokens, such as HTTP cookies or hidden fields in forms that are submitted using the POST method.

Request

GET /api/sharer.php?destination=digg&url=http%3A%2F%2Fwww.pfizer.com%2Fabout%2F&title=About%20Pfizer%20%7C%20Pfizer%3A%20the%20world's%20largest%20research-based%20pharmaceutical%20company&publisher=f5782661-29c9-43d9-81d8-7bdce05b3a3b&fpc=7639673-12c56ffa879-2f6d2c61-12&sessionID=1289949989299.31735&source=chicklet HTTP/1.1
Accept: */*
Referer: http://edge.sharethis.com/share4x/index.7dbd8c2c4a2160efef50761a91021817.html
Accept-Language: en-US
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)
Accept-Encoding: gzip, deflate
Host: wd.sharethis.com
Proxy-Connection: Keep-Alive
Cookie: __stid=CspST0zY2orBcjqxx2EuAg==

Response

HTTP/1.1 302 Found
Date: Tue, 16 Nov 2010 23:27:20 GMT
Server: Apache/2.2.14 (Ubuntu)
X-Powered-By: PHP/5.3.2-1ubuntu4.5
Location: http://digg.com/submit?phase=2&url=http%3A%2F%2Fwww.pfizer.com%2Fabout%2F&title=About+Pfizer+%7C+Pfizer%3A+the+world%27s+largest+research-based+pharmaceutical+company
Vary: Accept-Encoding
Connection: close
Content-Type: text/html; charset=utf-8
Content-Length: 0

3. HTML does not specify charset previous next

Summary

Severity:	Information
Confidence:	Certain
Host:	http://wd.sharethis.com
Path:	/api/getApi.php

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 /api/getApi.php?return=json&url=http%3A%2F%2Fwww.pfizer.com%2Fabout%2F&fpc=7639673-12c56ffa879-2f6d2c61-12&cb=initWidgetOnSuccess&service=initWidget HTTP/1.1
Accept: */*
Referer: http://edge.sharethis.com/share4x/index.7dbd8c2c4a2160efef50761a91021817.html
Accept-Language: en-US
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)
Accept-Encoding: gzip, deflate
Host: wd.sharethis.com
Proxy-Connection: Keep-Alive
Cookie: __stid=CspST0zY2orBcjqxx2EuAg==

Response

HTTP/1.1 200 OK
Date: Tue, 16 Nov 2010 23:27:14 GMT
Server: Apache/2.2.14 (Ubuntu)
X-Powered-By: PHP/5.3.2-1ubuntu4.5
Vary: Accept-Encoding
Connection: close
Content-Type: text/html
Content-Length: 112

initWidgetOnSuccess({"status":"SUCCESS","data":{"session_token":"958619bae76eae8c8a028e6e8d0586fc","ga":true}});

4. Content type incorrectly stated previous

Summary

Severity:	Information
Confidence:	Firm
Host:	http://wd.sharethis.com
Path:	/api/getApi.php

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 CSS.

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

Report generated by XSS.CX at Wed Nov 17 07:01:19 CST 2010.