XWiki Platform vulnerable to remote code execution through the section parameter in Administration as guest

Impact

XWiki doesn't properly escape the section URL parameter that is used in the code for displaying administration sections. This allows any user with read access to the document XWiki.AdminSheet (by default, everyone including unauthenticated users) to execute code including Groovy code. This impacts the confidentiality, integrity and availability of the whole XWiki instance.

By opening the URL <server>/xwiki/bin/get/Main/WebHome?sheet=XWiki.AdminSheet&viewer=content&section=%5D%5D%7B%7B%2Fhtml%7D%7D%7B%7Basync%7D%7D%7B%7Bgroovy%7D%7Dservices.logging.getLogger(%22attacker%22).error(%22Attack%20succeeded!%22)%7B%7B%2Fgroovy%7D%7D%7B%7B%2Fasync%7D%7D&xpage=view where <server> is the URL of the XWiki installation, it can be tested if an XWiki installation is vulnerable. If this causes a log message ERROR attacker - Attack succeeded! to appear in XWiki's log, the installation is vulnerable. In very old versions of XWiki, the attack can be demonstrated with <server>/xwiki/bin/get/XWiki/XWikiPreferences?section=%3C%25println(%22Hello%20from%20Groovy%22)%25%3E&xpage=view which displays admin.hello from groovy as title when the attack succeeds (tested on XWiki 1.7).

Patches

This vulnerability has been patched in XWiki 14.10.14, 15.6 RC1 and 15.5.1.

Workarounds

The fix, which consists of replacing = $services.localization.render("administration.sectionTitle$level", [$sectionName]) = by = $services.localization.render("administration.sectionTitle$level", 'xwiki/2.1', [$sectionName]) =, can be applied manually to the document XWiki.AdminSheet.

References

• https://jira.xwiki.org/browse/XWIKI-21110
• https://github.com/xwiki/xwiki-platform/commit/fec8e0e53f9fa2c3f1e568cc15b0e972727c803a