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 defences:
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.
1.1. https://hosting.intermedia.net/support/kb/ [name of an arbitrarily supplied request parameter]next
Summary
Severity:
High
Confidence:
Certain
Host:
https://hosting.intermedia.net
Path:
/support/kb/
Issue detail
The name of an arbitrarily supplied request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 4c275"><script>alert(1)</script>cebbf9c9140 was submitted in the name of an arbitrarily supplied request 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.
Request
GET /support/kb/?4c275"><script>alert(1)</script>cebbf9c9140=1 HTTP/1.1 Host: hosting.intermedia.net Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 200 OK Cache-Control: private Content-Length: 370 Content-Type: text/html; Charset=UTF-8 Server: Microsoft-IIS/7.0 X-Powered-By: ASP.NET Date: Mon, 03 Oct 2011 18:41:19 GMT Connection: close
The value of the 4c275 request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload ad25e"><script>alert(1)</script>a45d98bb273 was submitted in the 4c275 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.
1.3. https://hosting.intermedia.net/support/kb/default.asp [name of an arbitrarily supplied request parameter]previousnext
Summary
Severity:
High
Confidence:
Certain
Host:
https://hosting.intermedia.net
Path:
/support/kb/default.asp
Issue detail
The name of an arbitrarily supplied request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 69b76"><script>alert(1)</script>5ad2bea99e6 was submitted in the name of an arbitrarily supplied request 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.
The value of the 4c275 request parameter is copied into a JavaScript string which is encapsulated in double quotation marks. The payload 5aaa4"-alert(1)-"4e73069faa9 was submitted in the 4c275 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.
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.
1.5. https://hosting.intermedia.net/support/kb/printKBTreeNS.asp [name of an arbitrarily supplied request parameter]previousnext
Summary
Severity:
High
Confidence:
Certain
Host:
https://hosting.intermedia.net
Path:
/support/kb/printKBTreeNS.asp
Issue detail
The name of an arbitrarily supplied request parameter is copied into a JavaScript string which is encapsulated in double quotation marks. The payload b7d14"-alert(1)-"73f0f143f3d was submitted in the name of an arbitrarily supplied request 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.
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.
1.6. https://hosting.intermedia.net/support/kb/welcome.asp [name of an arbitrarily supplied request parameter]previousnext
Summary
Severity:
High
Confidence:
Certain
Host:
https://hosting.intermedia.net
Path:
/support/kb/welcome.asp
Issue detail
The name of an arbitrarily supplied request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 71653"><script>alert(1)</script>f803af305d9 was submitted in the name of an arbitrarily supplied request 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.
HTTP/1.1 200 OK Cache-Control: private Content-Type: text/html; Charset=UTF-8 Vary: Accept-Encoding Server: Microsoft-IIS/7.0 X-Powered-By: ASP.NET Date: Mon, 03 Oct 2011 18:43:25 GMT Content-Length: 13389
<HTML> <HEAD> <META NAME="description" CONTENT="Intermedia is a leading turnkey provider of advanced Shared and Dedicated Web and Exchange hosting solutions supporting ASP, ASP.NET ...[SNIP]... <script language="JavaScript" src="/support/kb/JavaScript/printHeader.js.asp?71653"><script>alert(1)</script>f803af305d9=1"> ...[SNIP]...
2. Cacheable HTTPS responsepreviousnext There are 5 instances of this issue:
Unless directed otherwise, browsers may store a local cached copy of content received from web servers. Some browsers, including Internet Explorer, cache content accessed via HTTPS. If sensitive information in application responses is stored in the local cache, then this may be retrieved by other users who have access to the same computer at a future time.
Issue remediation
The application should return caching directives instructing browsers not to store local copies of any sensitive data. Often, this can be achieved by configuring the web server to prevent caching for relevant paths within the web root. Alternatively, most web development platforms allow you to control the server's caching directives from within individual scripts. Ideally, the web server should return the following HTTP headers in all responses containing sensitive content:
GET /support/kb/ HTTP/1.1 Host: hosting.intermedia.net Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 200 OK Cache-Control: private Content-Length: 325 Content-Type: text/html; Charset=UTF-8 Server: Microsoft-IIS/7.0 X-Powered-By: ASP.NET Date: Mon, 03 Oct 2011 18:41:13 GMT Connection: close
HTTP/1.1 200 OK Cache-Control: private Content-Type: text/html; Charset=UTF-8 Vary: Accept-Encoding Server: Microsoft-IIS/7.0 X-Powered-By: ASP.NET Date: Mon, 03 Oct 2011 18:42:57 GMT Content-Length: 13344
<HTML> <HEAD> <META NAME="description" CONTENT="Intermedia is a leading turnkey provider of advanced Shared and Dedicated Web and Exchange hosting solutions supporting ASP, ASP.NET ...[SNIP]...
The response contains the following Content-type statement:
Content-Type: text/html; Charset=UTF-8
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.
