GHSA-vxwr-wpjv-qjq7 XWiki Platform: Privilege escalation (PR) from user registration through PDFClass

• Maven org.xwiki.platform:xwiki-platform-oldcore: >= 3.0.1, < 14.10.20 → fixed in 14.10.20 • Maven org.xwiki.platform:xwiki-platform-oldcore: >= 15.0-rc-1, < 15.5.4 → fixed in 15.5.4 • Maven org.xwiki.platform:xwiki-platform-oldcore: >= 15.6-rc-1, < 15.10-rc-1 → fixed in 15.10-rc-1

Impact Remote code execution is possible via PDF export templates. To reproduce on an installation, register a new user account with username `PDFClass` if `XWiki.PDFClass` does not exist. On `XWiki.PDFClass`, use the class editor to add a "style" property of type "TextArea" and content type "Plain Text". Then, add an object of class `PDFClass` and set the "style" attribute to `$services.logging.getLogger('PDFClass').error("I got programming: $services.security.authorization.hasAccess('programming')")`. Finally, go to `/xwiki/bin/export/Main/WebHome?format=pdf&pdftemplate=XWiki.PDFClass`. If the logs contain "ERROR PDFClass - I got programming: true", the instance is vulnerable. Patches This vulnerability has been patched in XWiki 14.10.20, 15.5.4 and 15.10-rc-1. Workarounds If PDF templates are not typically used on the instance, an administrator can create the document `XWiki.PDFClass` and block its edition, after making sure that it does not contain a `style` attribute. Otherwise, the instance needs to be updated. References • https://jira.xwiki.org/browse/XWIKI-21337 • https://github.com/xwiki/xwiki-platform/commit/d28e21a670c69880b951e415dd2ddd69d273eae9