XWiki Platform privilege escalation (PR) from account through AWM content fields

Impact

Any registered user can use the content field of their user profile page to execute arbitrary scripts with programming rights, thus effectively performing rights escalation.

The problem is present since version 4.3M2 when AppWithinMinutes Application added support for the Content field, allowing any wiki page (including the user profile page) to use its content as an AWM Content field, which has a custom displayer that executes the content with the rights of the AppWithinMinutes.Content author, rather than the rights of the content author.

Patches

The issue has been fixed in XWiki 14.10.5 and 15.1RC1 by https://github.com/xwiki/xwiki-platform/commit/dfb1cde173e363ca5c12eb3654869f9719820262 . The fix is in the content of the AppWithinMinutes.Content page that defines the custom displayer. By using the display script service to render the content we make sure that the proper author is used for access rights checks.

Workarounds

If you want to fix this problem on older versions of XWiki that have not been patched then you need to modify the content of AppWithinMinutes.Content page to use the display script service to render the content, like this:

- {{html}}$tdoc.getRenderedContent($tdoc.content, $tdoc.syntax.toIdString()).replace('{{', '{{'){{/html}}
+ {{html}}$services.display.content($tdoc, {
+   'displayerHint': 'default'
+ }).replace('{{/html}}', '{{/html}}'){{/html}}

References

• JIRA issue https://jira.xwiki.org/browse/XWIKI-19906
• Fix https://github.com/xwiki/xwiki-platform/commit/dfb1cde173e363ca5c12eb3654869f9719820262

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

Attribution

This vulnerability has been found and reported by @michitux .