XWiki Platform vulnerable to Cross-Site Scripting (XSS) through conflict resolution

Impact

By creating a conflict when another user with more rights is currently editing a page, it is possible to execute JavaScript snippets on the side of the other user, which compromises the confidentiality, integrity and availability of the whole XWiki installation.

To reproduce on a XWiki instance, a user with admin rights needs to edit a document without saving right away.
Then, as another user without any other right than edit on the specific document, change the whole content to <script>alert('XSS')</script>.
When the admin user then saves the document, a conflict popup appears. If they select “Fix each conflict individually” and see an alert displaying “XSS”, then the instance is vulnerable.

Patches

This has been patched in XWiki 15.10.8 and 16.3.0RC1.

Workarounds

We’re not aware of any workaround except upgrading.

References

• https://jira.xwiki.org/browse/XWIKI-21626
• https://github.com/xwiki/xwiki-platform/commit/821d43ec45e67d45a6735a0717b9b77fffc1cd9f

For more information

If you have any questions or comments about this advisory:

• Open an issue in Jira XWiki.org
• Email us at Security Mailing List