CVE-2025-13365 identifies a Cross-Site Request Forgery (CSRF) vulnerability in the WP Hallo Welt plugin for WordPress, affecting all versions up to 1.4. The root cause is the absence or incorrect implementation of nonce validation in the 'hallo_welt_seite' function, which is responsible for handling certain plugin settings or actions. Nonces in WordPress are security tokens used to verify that requests originate from legitimate users and not from forged sources. Without proper nonce checks, attackers can craft malicious web requests that, when executed by an authenticated administrator (via clicking a link or visiting a malicious page), cause unauthorized changes to plugin settings. Additionally, the plugin suffers from insufficient input sanitization and output escaping, enabling stored Cross-Site Scripting (XSS) attacks. This means malicious scripts injected via the plugin settings can persist and execute in the browsers of site visitors or administrators, potentially leading to session hijacking, data theft, or further compromise. The CVSS 3.1 base score is 6.1 (medium), reflecting network attack vector, low attack complexity, no privileges required, but user interaction needed, and a scope change due to impact beyond the vulnerable component. No patches or known exploits are currently available, but the vulnerability poses a significant risk to WordPress sites using this plugin, especially those with administrative users who might be targeted for social engineering. The vulnerability was publicly disclosed on December 20, 2025, with the CVE reserved about a month earlier.

For European organizations, this vulnerability can lead to unauthorized modification of website content and settings, potentially resulting in defacement, data leakage, or persistent malicious code execution affecting site visitors and administrators. Organizations relying on WordPress with the WP Hallo Welt plugin are at risk of compromised website integrity and confidentiality. Stored XSS can facilitate session hijacking or malware distribution, impacting customer trust and regulatory compliance, especially under GDPR where data breaches must be reported. The attack requires tricking an administrator, so organizations with less stringent user awareness or lacking multi-factor authentication on admin accounts are more vulnerable. The disruption to website availability is minimal, but reputational damage and potential legal consequences from data exposure are significant. Given WordPress's widespread use in Europe, especially among SMEs and public sector websites, the impact can be broad if not mitigated promptly.

Immediate mitigation steps include disabling or uninstalling the WP Hallo Welt plugin until a security patch is released. Administrators should be trained to recognize phishing and social engineering attempts to prevent inadvertent execution of malicious requests. Implementing strict Content Security Policies (CSP) can help mitigate the impact of stored XSS. Enforcing multi-factor authentication (MFA) for WordPress admin accounts reduces the risk of account compromise. Monitoring web server logs for unusual POST requests targeting the plugin’s endpoints can help detect exploitation attempts. Web Application Firewalls (WAFs) should be configured to block suspicious CSRF patterns or anomalous requests to the plugin’s functions. Developers or site maintainers should apply nonce validation and proper input sanitization/output escaping in the plugin code as soon as a patch is available. Regular backups and incident response plans should be updated to handle potential exploitation scenarios.