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 value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 7d6a2"><a>83db860ccc8 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 /document7d6a2"><a>83db860ccc8/questmark-leads-17m-for-utest/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
The value of REST URL parameter 2 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 98168"><img%20src%3da%20onerror%3dalert(1)>365e5e0b4be was submitted in the REST URL parameter 2. This input was echoed as 98168"><img src=a onerror=alert(1)>365e5e0b4be 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 /document/questmark-leads-17m-for-utest98168"><img%20src%3da%20onerror%3dalert(1)>365e5e0b4be/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
1.3. http://www.crowdsourcing.org/document/questmark-leads-17m-for-utest/8992 [name of an arbitrarily supplied request parameter]previousnext
Summary
Severity:
High
Confidence:
Certain
Host:
http://www.crowdsourcing.org
Path:
/document/questmark-leads-17m-for-utest/8992
Issue detail
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 ddc06"><script>alert(1)</script>80db1c3dd9d was submitted in the name of an arbitrarily supplied request parameter. This input was echoed unmodified in the application's response.
This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.
Request
GET /document/questmark-leads-17m-for-utest/8992?ddc06"><script>alert(1)</script>80db1c3dd9d=1 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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 ad1c5"><a>f29e274d210 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 /editorialad1c5"><a>f29e274d210/changing-the-paradigm-utests-model-for-crowd-management/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
The value of REST URL parameter 2 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload cdb74"><img%20src%3da%20onerror%3dalert(1)>2b0348a80cf was submitted in the REST URL parameter 2. This input was echoed as cdb74"><img src=a onerror=alert(1)>2b0348a80cf 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 /editorial/changing-the-paradigm-utests-model-for-crowd-managementcdb74"><img%20src%3da%20onerror%3dalert(1)>2b0348a80cf/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
1.6. http://www.crowdsourcing.org/editorial/changing-the-paradigm-utests-model-for-crowd-management/3994 [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 31d00"><script>alert(1)</script>f506c00517b was submitted in the name of an arbitrarily supplied request parameter. This input was echoed unmodified in the application's response.
This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.
Request
GET /editorial/changing-the-paradigm-utests-model-for-crowd-management/3994?31d00"><script>alert(1)</script>f506c00517b=1 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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.
The page contains a form with the following action URL, which is submitted over clear-text HTTP:
http://www.crowdsourcing.org/login/process
The form contains the following password field:
password
Request
GET /document/questmark-leads-17m-for-utest/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
The page contains a form with the following action URL, which is submitted over clear-text HTTP:
http://www.crowdsourcing.org/login/process
The form contains the following password field:
password
Request
GET /editorial/changing-the-paradigm-utests-model-for-crowd-management/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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 fulfill, 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.
GET /document/questmark-leads-17m-for-utest/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
GET /editorial/changing-the-paradigm-utests-model-for-crowd-management/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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 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 /document/questmark-leads-17m-for-utest/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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 /editorial/changing-the-paradigm-utests-model-for-crowd-management/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
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).
The following email address was disclosed in the response:
tips@crowdsourcing.org
Request
GET /document/questmark-leads-17m-for-utest/8992 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
The following email address was disclosed in the response:
tips@crowdsourcing.org
Request
GET /editorial/changing-the-paradigm-utests-model-for-crowd-management/3994 HTTP/1.1 Host: www.crowdsourcing.org Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close