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 REST URL parameter 1 is copied into the value of an HTML tag attribute which is not encapsulated in any quotation marks. The payload e29ee%20a%3db3a4ec9bbad8 was submitted in the REST URL parameter 1. This input was echoed as e29ee a=b3a4ec9bbad8 in the application's response.
This behaviour demonstrates that it is possible to inject new attributes into an existing HTML tag. 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 /etailusaeaste29ee%20a%3db3a4ec9bbad8/ HTTP/1.1 Host: www.wbresearch.com 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 Connection: close Date: Sat, 11 Dec 2010 02:06:29 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET X-AspNet-Version: 2.0.50727 Set-Cookie: ecm=user_id=0&isMembershipUser=0&site_id=&username=&new_site=/&unique_id=0&site_preview=0&langvalue=0&DefaultLanguage=1033&NavLanguage=1033&LastValidLanguageID=1033&ContType=&UserCulture=1033&dm=www.wbresearch.com&SiteLanguage=1033; path=/ Set-Cookie: ASP.NET_SessionId=fkbwoe45wgiga045hcbxa2vx; path=/; HttpOnly Cache-Control: private Content-Type: text/html; charset=utf-8 Content-Length: 36866
The value of REST URL parameter 1 is copied into the value of an HTML tag attribute which is not encapsulated in any quotation marks. The payload f8351%20a%3db39f7a5ea6ae was submitted in the REST URL parameter 1. This input was echoed as f8351 a=b39f7a5ea6ae in the application's response.
This behaviour demonstrates that it is possible to inject new attributes into an existing HTML tag. 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 /luxuryinteractivef8351%20a%3db39f7a5ea6ae/agenda_main_full2.asp HTTP/1.1 Host: www.wbresearch.com 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 Connection: close Date: Sat, 11 Dec 2010 02:06:07 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET X-AspNet-Version: 2.0.50727 Set-Cookie: ecm=user_id=0&isMembershipUser=0&site_id=&username=&new_site=/&unique_id=0&site_preview=0&langvalue=0&DefaultLanguage=1033&NavLanguage=1033&LastValidLanguageID=1033&ContType=&UserCulture=1033&dm=www.wbresearch.com&SiteLanguage=1033; path=/ Set-Cookie: ASP.NET_SessionId=3wymaje20jlcuf2yy5zas1mn; path=/; HttpOnly Cache-Control: private Content-Type: text/html; charset=utf-8 Content-Length: 36892
The value of REST URL parameter 2 is copied into the value of an HTML tag attribute which is not encapsulated in any quotation marks. The payload f2ef6%20a%3db5edbd6eed74 was submitted in the REST URL parameter 2. This input was echoed as f2ef6 a=b5edbd6eed74 in the application's response.
This behaviour demonstrates that it is possible to inject new attributes into an existing HTML tag. 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 /luxuryinteractive/f2ef6%20a%3db5edbd6eed74 HTTP/1.1 Host: www.wbresearch.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response (redirected)
HTTP/1.1 200 OK Connection: close Date: Sat, 11 Dec 2010 02:06:10 GMT Server: Microsoft-IIS/6.0 X-Powered-By: ASP.NET X-AspNet-Version: 2.0.50727 Set-Cookie: ecm=user_id=0&isMembershipUser=0&site_id=&username=&new_site=/&unique_id=0&site_preview=0&langvalue=0&DefaultLanguage=1033&NavLanguage=1033&LastValidLanguageID=1033&ContType=&UserCulture=1033&dm=www.wbresearch.com&SiteLanguage=1033; path=/ Set-Cookie: ASP.NET_SessionId=3mnxfl3ufxhafyzlzdbsh255; path=/; HttpOnly Cache-Control: private Content-Type: text/html; charset=utf-8 Content-Length: 36872