XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. XWiki is vulnerable to a remote code execution (RCE) attack through its user registration feature. This issue allows an attacker to execute arbitrary code by crafting malicious payloads in the "first name" or "last name" fields during user registration. This impacts all installations that have user registration enabled for guests. This vulnerability has been patched in XWiki 14.10.17, 15.5.3 and 15.8 RC1.