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.
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 65415<script>alert(1)</script>00f8bf339e4 was submitted in the REST URL parameter 1. 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.
Note that a redirection occurred between the attack request and the response containing the echoed input. It is necessary to follow this redirection for the attack to succeed. When the attack is carried out via a browser, the redirection will be followed automatically.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /archives65415<script>alert(1)</script>00f8bf339e4/press/2011/07/july-ratings-fo.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 2 is copied into the HTML document as plain text between tags. The payload 67850<script>alert(1)</script>474622dc94 was submitted in the REST URL parameter 2. 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.
Note that a redirection occurred between the attack request and the response containing the echoed input. It is necessary to follow this redirection for the attack to succeed. When the attack is carried out via a browser, the redirection will be followed automatically.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /archives/press67850<script>alert(1)</script>474622dc94/2011/07/july-ratings-fo.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 3 is copied into the HTML document as plain text between tags. The payload 91bd3<script>alert(1)</script>16b9f6cc4f8 was submitted in the REST URL parameter 3. 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.
Note that a redirection occurred between the attack request and the response containing the echoed input. It is necessary to follow this redirection for the attack to succeed. When the attack is carried out via a browser, the redirection will be followed automatically.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /archives/press/201191bd3<script>alert(1)</script>16b9f6cc4f8/07/july-ratings-fo.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 4 is copied into the HTML document as plain text between tags. The payload b3374<script>alert(1)</script>04d570ae265 was submitted in the REST URL parameter 4. 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.
Note that a redirection occurred between the attack request and the response containing the echoed input. It is necessary to follow this redirection for the attack to succeed. When the attack is carried out via a browser, the redirection will be followed automatically.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /archives/press/2011/07b3374<script>alert(1)</script>04d570ae265/july-ratings-fo.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 5 is copied into the HTML document as plain text between tags. The payload f1060<script>alert(1)</script>cc48727f5a7 was submitted in the REST URL parameter 5. 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.
Note that a redirection occurred between the attack request and the response containing the echoed input. It is necessary to follow this redirection for the attack to succeed. When the attack is carried out via a browser, the redirection will be followed automatically.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /archives/press/2011/07/july_ratings_fo.htmlf1060<script>alert(1)</script>cc48727f5a7 was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 7421a<script>alert(1)</script>69beae88348 was submitted in the REST URL parameter 1. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /favicon.ico7421a<script>alert(1)</script>69beae88348 was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 2c233<script>alert(1)</script>fa121270a17 was submitted in the REST URL parameter 1. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandora2c233<script>alert(1)</script>fa121270a17/ was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload a63a9<script>alert(1)</script>b432026ab83 was submitted in the REST URL parameter 1. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandoraa63a9<script>alert(1)</script>b432026ab83/archives/2011/08/an-update-on-th.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 2 is copied into the HTML document as plain text between tags. The payload a2452<script>alert(1)</script>704154660ed was submitted in the REST URL parameter 2. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandora/archivesa2452<script>alert(1)</script>704154660ed/2011/08/an-update-on-th.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 3 is copied into the HTML document as plain text between tags. The payload 31243<script>alert(1)</script>29836ab1e86 was submitted in the REST URL parameter 3. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandora/archives/201131243<script>alert(1)</script>29836ab1e86/08/an-update-on-th.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 4 is copied into the HTML document as plain text between tags. The payload c69b9<script>alert(1)</script>867f2bdcfa5 was submitted in the REST URL parameter 4. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandora/archives/2011/08c69b9<script>alert(1)</script>867f2bdcfa5/an-update-on-th.html was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 5 is copied into the HTML document as plain text between tags. The payload 2cd87<script>alert(1)</script>371995b80c8 was submitted in the REST URL parameter 5. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /pandora/archives/2011/08/an-update-on-th.html2cd87<script>alert(1)</script>371995b80c8 was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 29f3f<script>alert(1)</script>a0f483d67b was submitted in the REST URL parameter 1. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /press29f3f<script>alert(1)</script>a0f483d67b was not found on this server.</p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 1c135<script>alert(1)</script>8f8d8684215 was submitted in the REST URL parameter 1. 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.
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /press1c135<script>alert(1)</script>8f8d8684215/ was not found on this server.</p> ...[SNIP]...
2. Cross-domain script includepreviousnext There are 3 instances of this issue:
When an application includes a script from an external domain, this script is executed by the browser within the security context of the invoking application. The script can therefore do anything that the application's own scripts can do, such as accessing application data and performing actions within the context of the current user.
If you include a script from an external domain, then you are trusting that domain with the data and functionality of your application, and you are trusting the domain's own security to prevent an attacker from modifying the script to perform malicious actions within your application.
Issue remediation
Scripts should not be included from untrusted domains. If you have a requirement which a third-party script appears to fulfil, then you should ideally copy the contents of that script onto your own domain and include it from there. If that is not possible (e.g. for licensing reasons) then you should consider reimplementing the script's functionality within your own code.
The TRACE method is designed for diagnostic purposes. If enabled, the web server will respond to requests which use the TRACE method by echoing in its response the exact request which was received.
Although this behaviour is apparently harmless in itself, it can sometimes be leveraged to support attacks against other application users. If an attacker can find a way of causing a user to make a TRACE request, and can retrieve the response to that request, then the attacker will be able to capture any sensitive data which is included in the request by the user's browser, for example session cookies or credentials for platform-level authentication. This may exacerbate the impact of other vulnerabilities, such as cross-site scripting.
Issue remediation
The TRACE method should be disabled on the web server.
The presence of email addresses within application responses does not necessarily constitute a security vulnerability. Email addresses may appear intentionally within contact information, and many applications (such as web mail) include arbitrary third-party email addresses within their core content.
However, email addresses of developers and other individuals (whether appearing on-screen or hidden within page source) may disclose information that is useful to an attacker; for example, they may represent usernames that can be used at the application's login, and they may be used in social engineering attacks against the organisation's personnel. Unnecessary or excessive disclosure of email addresses may also lead to an increase in the volume of spam email received.
Issue remediation
You should review the email addresses being disclosed by the application, and consider removing any that are unnecessary, or replacing personal addresses with anonymous mailbox addresses (such as helpdesk@example.com).
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content- ...[SNIP]... <p>Ir you are experiencing technical difficulties with the new site, please send us an email at pandora-support@pandora.com so we can provide you with specific assistance.</p> ...[SNIP]... <p>Remember, if you're having trouble with getting the new Pandora.com to work or any other technical aspect of Pandora please send us an email at pandora-support@pandora.com and we'll get back to you within 24 hours.</p> ...[SNIP]... <p>Hope some of this helps. Remember, if you're having any technical problems send an email to pandora-support@pandora.com so we can help you out personally.</p> ...[SNIP]...
/* * Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) * and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses. * * $LastChangedDate$ * $Rev$ */ ...[SNIP]... the chain. If passed in the * chain will not be broken and the result will be assigned to this object. * @type Object * @cat Plugins/Dimensions * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net) */ jQuery.fn.offset = function(options, returnObject) { var x = 0, y = 0, elem = this[0], parent = this[0], sl = 0, st = 0, options = jQuery.extend({ margin: true, border ...[SNIP]...
/* * Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) * and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses. * * $LastChangedDate$ * $Rev$ */ ...[SNIP]... the chain. If passed in the * chain will not be broken and the result will be assigned to this object. * @type Object * @cat Plugins/Dimensions * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net) */ jQuery.fn.offset = function(options, returnObject) { var x = 0, y = 0, elem = this[0], parent = this[0], sl = 0, st = 0, options = jQuery.extend({ margin: true, border ...[SNIP]...
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.
