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 organization. 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 organization 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 organization 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 sanitized.
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 ce466<a>d542f2235bc was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
Request
GET /apice466<a>d542f2235bc/search/index/online/query/{QUERY} HTTP/1.1 Host: search.champlain.edu Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 404 Not Found Date: Mon, 26 Dec 2011 12:08:35 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 7041 Connection: close Content-Type: text/html; charset=UTF-8
<!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-T ...[SNIP]... </b> Invalid controller specified (apice466<a>d542f2235bc) </p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload c0240<a>e5a16831ba0 was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
The value of the callback request parameter is copied into a JavaScript expression which is not encapsulated in any quotation marks. The payload e467b%3balert(1)//f9f1af4badf was submitted in the callback parameter. This input was echoed as e467b;alert(1)//f9f1af4badf 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.
HTTP/1.1 200 OK Date: Sun, 25 Dec 2011 21:07:04 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 2467 Connection: close Content-Type: application/json
dojo.io.script.jsonp_dojoIoScript3._jsonpCallbacke467b;alert(1)//f9f1af4badf({"identifier":"id","items":[{"id":"b4","body":"Use the Online Incident Reporting System Form to report general incidents, concerning or threatening behavior, medical transport, police report, public s ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 33159<a>c50595397ad was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
The value of the callback request parameter is copied into a JavaScript expression which is not encapsulated in any quotation marks. The payload 273c4%3balert(1)//300294447de was submitted in the callback parameter. This input was echoed as 273c4;alert(1)//300294447de 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.
HTTP/1.1 200 OK Date: Sun, 25 Dec 2011 21:06:13 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 169 Connection: close Content-Type: application/json
dojo.io.script.jsonp_dojoIoScript1._jsonpCallback273c4;alert(1)//300294447de({"identifier":"id","items":[{"id":"error","error_message":"No pages matched your query."}]})
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload a1c2c<a>b589f97c32 was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
Request
GET /apia1c2c<a>b589f97c32/search/index/www/query/{QUERY} HTTP/1.1 Host: search.champlain.edu Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 404 Not Found Date: Mon, 26 Dec 2011 12:08:29 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 7036 Connection: close Content-Type: text/html; charset=UTF-8
<!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-T ...[SNIP]... </b> Invalid controller specified (apia1c2c<a>b589f97c32) </p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 828b1<a>9bf0dd28440 was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 5aaab<a>726a1d76ac7 was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
Request
GET /favicon.ico5aaab<a>726a1d76ac7 HTTP/1.1 Host: search.champlain.edu User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.13) Gecko/20110504 Namoroka/3.6.13 Accept: image/png,image/*;q=0.8,*/*;q=0.5 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 115 Proxy-Connection: keep-alive Content-Length: 10
Response
HTTP/1.1 404 Not Found Date: Sun, 25 Dec 2011 21:05:53 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 7003 Connection: close Content-Type: text/html; charset=UTF-8
<!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-T ...[SNIP]... </b> Invalid controller specified (favicon.ico5aaab<a>726a1d76ac7) </p> ...[SNIP]...
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 38f08<a>cfaf9fa63c6 was submitted in the REST URL parameter 1. This input was echoed unmodified in the application's response.
This behaviour demonstrates that it is possible to inject new HTML tags into the returned document. An attempt was made to identify a full proof-of-concept attack for injecting arbitrary JavaScript but this was not successful. You should manually examine the application's behaviour and attempt to identify any unusual input validation or other obstacles that may be in place.
Request
GET /favicon.ico5aaab%3Ca%3E726a1d76ac738f08<a>cfaf9fa63c6?xss=9 HTTP/1.1 Host: search.champlain.edu User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.13) Gecko/20110504 Namoroka/3.6.13 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip,deflate Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive: 115 Proxy-Connection: keep-alive Content-Length: 10
Response
HTTP/1.1 404 Not Found Date: Sun, 25 Dec 2011 21:08:03 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 7068 Connection: close Content-Type: text/html; charset=UTF-8
<!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-T ...[SNIP]... </b> Invalid controller specified (favicon.ico5aaab%3Ca%3E726a1d76ac738f08<a>cfaf9fa63c6) </p> ...[SNIP]...
The following email addresses were disclosed in the response:
HelpDesk@champlain.edu
MediaServices@champlain.edu
helpdesk@champlain.edu
Issue background
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 organization'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).
HTTP/1.1 200 OK Date: Sun, 25 Dec 2011 21:06:58 GMT Server: Apache/2.2.3 (Red Hat) X-Powered-By: PHP/5.3.8 Vary: Accept-Encoding Content-Length: 2440 Connection: close Content-Type: application/json
dojo.io.script.jsonp_dojoIoScript3._jsonpCallback({"identifier":"id","items":[{"id":"b4","body":"Use the Online Incident Reporting System Form to report general incidents, concerning or threatening be ...[SNIP]... <a href=\"mailto:helpdesk@champlain.edu\">HelpDesk@champlain.edu<\/a> ...[SNIP]... <a href=\"mailto:MediaServices@champlain.edu\">MediaServices@champlain.edu<\/a> ...[SNIP]...
Report generated by HTI at Sat Sep 01 09:26:49 EDT 2012.