CVE-2026-105881: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in ThemeGrill User Registration

The ThemeGrill User Registration plugin suffers from a stored cross-site scripting vulnerability due to improper neutralization of input during web page generation. This allows attackers with at least low privileges and requiring user interaction to inject malicious scripts that persist in the application. The vulnerability affects all versions from initial release up to but not including 5.3.0. The CVSS 3.1 vector indicates network attack vector, low attack complexity, low privileges required, user interaction required, scope changed, and impacts on confidentiality, integrity, and availability at low levels.

Successful exploitation can lead to persistent injection of malicious scripts, potentially allowing attackers to execute arbitrary scripts in the context of affected users. This can result in partial compromise of confidentiality, integrity, and availability of the affected system or user data. The attack requires user interaction and low privileges, and the scope of impact extends beyond the vulnerable component.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, consider restricting user input or applying web application firewall rules to detect and block malicious payloads related to stored XSS in the User Registration plugin.