Impact Its possible to know if a user has or not an account in a wiki related to an email address, and which username(s) is actually tied to that email by forging a request to the Forgot username page. Note that since this page does not have a CSRF check its quite easy to perform a lot of those requests. ### Patches This issue has been patched in XWiki 12.10.5 and 13.2RC1. Two different patches are provided: - a first one to fix the CSRF problem - a more complex one that now relies on sending an email for the Forgot username process. ### Workarounds Its possible to fix the problem without uprading by editing the ForgotUsername page in version below 13.x, to use the following code: https://github.com/xwiki/xwiki-platform/blob/69548c0320cbd772540cf4668743e69f879812cf/xwiki-platform-core/xwiki-platform-administration/xwiki-platform-administration-ui/src/main/resources/XWiki/ForgotUsername.xml#L39-L123 In version after 13.x its also possible to edit manually the forgotusername.vm file, but its really encouraged to upgrade the version here. ### References * https://jira.xwiki.org/browse/XWIKI-18384 * https://jira.xwiki.org/browse/XWIKI-18408 ### For more information If you have any questions or comments about this advisory: * Open an issue in Jira XWiki * Email us at security ML
Weakness
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Xwiki |
Xwiki |
* |
12.10.5 (excluding) |
| Xwiki |
Xwiki |
13.0 (including) |
13.0 (including) |
| Xwiki |
Xwiki |
13.1 (including) |
13.1 (including) |
Potential Mitigations
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, use anti-CSRF packages such as the OWASP CSRFGuard. [REF-330]
- Another example is the ESAPI Session Management control, which includes a component for CSRF. [REF-45]
- Use the “double-submitted cookie” method as described by Felten and Zeller:
- When a user visits a site, the site should generate a pseudorandom value and set it as a cookie on the user’s machine. The site should require every form submission to include this value as a form value and also as a cookie value. When a POST request is sent to the site, the request should only be considered valid if the form value and the cookie value are the same.
- Because of the same-origin policy, an attacker cannot read or modify the value stored in the cookie. To successfully submit a form on behalf of the user, the attacker would have to correctly guess the pseudorandom value. If the pseudorandom value is cryptographically strong, this will be prohibitively difficult.
- This technique requires Javascript, so it may not work for browsers that have Javascript disabled. [REF-331]
References