Security Alert: Cross-site scripting vulnerability with TWiki URLPARAM variable
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This advisory alerts you of a potential security issue with your TWiki installation: The %URLPARAM{}% TWiki variable may expose a cross-site scripting (XSS) vulnerability. (See also unrelated
SecurityAlert-CVE-2008-5305 - TWiki SEARCH variable allows arbitrary shell command execution.)
Vulnerable Software Version
Attack Vectors
Editing wiki pages and HTTP GET requests towards the wiki server (typically port 80/TCP). Typically, prior authentication is necessary (including anonymous TWikiGuest accounts).
Impact
An unauthenticated remote attacker could exploit an XSS attack on a TWiki site.
Severity Level
The TWiki
SecurityTeam triaged this issue as documented in
TWikiSecurityAlertProcess and assigned the following severity level:
- Severity 3 issue: TWiki content or browser is compromised
Note: Severity 3 issues are usually handled as bugs without an advisory, but this time an advisory is issued to raise the awareness on possible XSS attacks.
MITRE Name for this Vulnerability
The Common Vulnerabilities and Exposures project has assigned the name
CVE-2008-5304 to this vulnerability.
Details
The %URLPARAM{}% TWiki variable is a powerful command to create dynamic wiki content and wiki applications. If a URLPARAM is not properly encoded it may be open to XSS attacks.
http://en.wikipedia.org/wiki/Cross-site_scripting has details on XSS.
Specifically, the XSS vulnerability exists if the URLPARAM is used inside an
HTML form field value without adding proper encoding. Example:
<input type="text" name="city" value="%URLPARAM{ "city" }%" />
The attacker could construct a 'city' URL parameter with a double quote to close the input value="" attribute, followed by additional attributes.
Example 1:
- Go to
http://example.com/twiki/view/TWiki/WebSearch?search=%27a%20onmouseover=alert(document.cookie)%20%27
- Move your mouse over the 'Advanced search' link about half way down the page.
- You should see a javascript popup that wasn't there before.
Example 2:
- Go to
http://example.com/twiki/view/TWiki/ResetPassword?username="<script language=Javascript>alert('3y3 0wn j00 TWIKI')</script>
- You should see a javascript popup that wasn't there before.
To avoid XSS attacks, a URLPARAM inside a
HTML form field value needs to be entity encoded. This will escape special characters, so that content will be displayed verbatim in the input field. Example of properly encoding a URLPARAM in an input field value:
<input type="text" name="city" value="%URLPARAM{ "city" encode="entity" }%" />
The TWiki distributions contains a number of pages that have non-encoded URLPARAMs in
HTML input fields. Those pages need to be fixed to avoid XSS attacks.
One might think that URLPARAM should always be encoded. This is not a viable option since it would introduce an incompatible spec change that would break many dynamic reports and TWiki applications.
The responsibility relies with the users to monitor and/or lock down wiki content to counter XSS exploits. Study
http://twiki.org/cgi-bin/view/TWiki/VarURLPARAM on proper use of URLPARAM.
Countermeasures
- Apply hotfix (see patch below).
- Upgrade to the latest patched production TWiki-4.2.4, TWikiRelease04x02x04.
- Use the web server software to restrict access to the web pages served by TWiki.
- Search your wiki content for
%URLPARAM
and encode them where needed.
Authors and Credits
Hotfix for TWiki Production Release 4.2.x
Affected files:
-
twiki/data/TWiki/ChangePassword.txt
-
twiki/data/TWiki/ChangePassword.txt,v
-
twiki/data/TWiki/FormattedSearch.txt
-
twiki/data/TWiki/FormattedSearch.txt,v
-
twiki/data/TWiki/ResetPassword.txt
-
twiki/data/TWiki/ResetPassword.txt,v
-
twiki/data/TWiki/VarURLPARAM.txt
-
twiki/data/TWiki/VarURLPARAM.txt,v
-
twiki/data/TWiki/WebAtomBase.txt
-
twiki/data/TWiki/WebAtomBase.txt,v
-
twiki/data/TWiki/WebCreateNewTopicTemplate.txt
-
twiki/data/TWiki/WebCreateNewTopicTemplate.txt,v
-
twiki/data/TWiki/WebRssBase.txt
-
twiki/data/TWiki/WebRssBase.txt,v
-
twiki/data/TWiki/WebSearchAdvanced.txt
-
twiki/data/TWiki/WebSearchAdvanced.txt,v
-
twiki/data/TWiki/WebSearch.txt
-
twiki/data/TWiki/WebSearch.txt,v
Hotfix: Unzip
SecurityAlert-CVE-2008-5304-hotfix.zip into your TWiki directory, preserving the directory structure. All files should go into the
twiki/data/TWiki
directory.
Fixing older TWiki Releases
There is no hotfix for older releases. Upgrade to the latest TWiki version, or search your wiki content for
%URLPARAM
and encode them where needed.
Action Plan with Timeline
# |
Action |
Date/ Deadline |
Status |
Who |
1. |
User discloses issue to TWikiSecurityMailingList |
2008-11-18 |
Done |
Marc Schoenefeld |
2. |
Developer verifies issue |
2008-11-27 |
Done |
Peter Thoeny |
3. |
Developer fixes code |
2008-12-01 |
Done |
Peter Thoeny, Sopan Shewale |
4. |
Security team creates advisory with hotfix |
2008-12-03 |
Done |
Peter Thoeny |
5. |
Send alert to TWikiAnnounceMailingList and TWikiDevMailingList |
2008-12-03 |
Done |
Peter Thoeny |
6. |
Publish advisory in Codev web and update all related topics |
2008-12-05 |
Done |
Peter Thoeny |
7. |
Issue a public security advisory (vuln@secunia.com, cert@cert.org, bugs@securitytracker.com, full-disclosure@lists.netsys.com, vulnwatch@vulnwatch.org) |
2008-12-05 |
Done |
Peter Thoeny |
External Links
--
PeterThoeny - 03 Dec 2008
Discussions
While it's understandable that the 3-Dec announcemet had the .zip file stripped by mailman, this negated the benefit of the pre-announcement.
The announcement should have provided a link to the .zip file.
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TimotheLitt - 06 Dec 2008
Good point on stripped e-mail attachments. The
SecurityTeam will keep this in mind for next time (if any). The team is quite responsive, you can send an e-mail to the
TWikiSecurityMailingList if your question needs immediate attention.
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PeterThoeny - 07 Dec 2008