CVE-2023-29513: 
Java vulnerability analysis and mitigation

XWiki Platform, a generic wiki platform offering runtime services for applications, was found to contain a vulnerability (CVE-2023-29513) that allows unauthorized user creation. The vulnerability affects versions from 8.0-rc-1 up to versions before 15.0-rc-1 and 14.10.1. If a guest has view rights on any document, they can exploit the vulnerability to create new users even when registration is disabled by using the distribution/firstadminuser.wiki template in the wrong context (GitHub Advisory).

The vulnerability exists in the template macro functionality of XWiki Platform. An attacker can exploit this by accessing a specific URL with crafted parameters that invoke the template macro with the distribution/firstadminuser.wiki template. Starting with XWiki 14.5 (or CKEditor contrib extension 1.64.3), a valid CSRF token is required for exploitation. The vulnerability has been assigned a CVSS v3.1 score of 5.0 (Medium) with the vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N, indicating it requires network access and low privileges but can affect resources beyond its security scope (GitHub Advisory).

The vulnerability allows unauthorized users to bypass registration restrictions and create new user accounts without proper validation. This could lead to unauthorized access to the system and potential privilege escalation. The vulnerability specifically affects wikis that have view rights for guests but have user registration disabled (GitHub Advisory).

The vulnerability can be exploited by accessing a specific URL pattern as a guest user. The attacker needs view rights on any document to execute the exploit. The attack involves using the CKEditor.HTMLConverter sheet with specific parameters to invoke the vulnerable template. A proof of concept exists and has been documented in the advisory (GitHub Advisory).

The vulnerability has been patched in XWiki versions 15.0-rc-1 and 14.10.1. There are no known workarounds other than upgrading to a patched version. Users are strongly advised to upgrade to these versions or later to address the security issue (GitHub Advisory).