CVE-2025-11811 is a stored cross-site scripting (XSS) vulnerability identified in the Simple Youtube Shortcode plugin for WordPress, affecting all versions up to and including 1.1.3. The vulnerability stems from improper neutralization of input during web page generation, specifically insufficient sanitization and escaping of the 'id' attribute within the 'embed_youtube' shortcode. This flaw allows authenticated users with contributor-level access or higher to inject arbitrary JavaScript code into WordPress pages. When other users access these pages, the malicious scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, or unauthorized actions within the context of the affected site. The vulnerability has a CVSS v3.1 base score of 6.4, reflecting medium severity, with an attack vector of network, low attack complexity, requiring privileges (PR:L), no user interaction, and a scope change (S:C). The impact affects confidentiality and integrity but not availability. No public exploits have been reported yet, but the vulnerability poses a risk due to the widespread use of WordPress and the plugin's functionality that allows embedding YouTube videos via shortcodes. The vulnerability was published on October 22, 2025, with no patches currently available, emphasizing the need for immediate mitigation steps. The CWE classification is CWE-79, indicating cross-site scripting due to improper input handling.

For European organizations, this vulnerability can lead to unauthorized script execution within their WordPress sites, compromising user sessions, leaking sensitive information, or enabling further attacks such as phishing or malware distribution. Organizations relying on the Simple Youtube Shortcode plugin for content embedding are particularly vulnerable if contributor-level users are present, as they can exploit this flaw to inject malicious code. This can damage organizational reputation, lead to data breaches, and disrupt user trust. Since WordPress powers a significant portion of websites in Europe, including corporate, governmental, and media sites, the potential impact is broad. The vulnerability's exploitation could also facilitate lateral movement within networks if administrative credentials are compromised. However, the requirement for authenticated contributor access limits the attack surface somewhat, reducing risk from external unauthenticated attackers. Still, insider threats or compromised contributor accounts increase the risk significantly.

European organizations should immediately audit user roles and permissions within WordPress, limiting contributor-level access to trusted individuals only. Implement strict input validation and output escaping for any shortcode or user-generated content, possibly by applying custom filters or security plugins that sanitize inputs. Monitor and log shortcode usage and page content changes to detect suspicious script injections early. Until an official patch is released, consider disabling the Simple Youtube Shortcode plugin or replacing it with alternative, secure plugins that provide similar functionality. Conduct regular vulnerability scans and penetration tests focusing on XSS vectors in WordPress environments. Educate content contributors about security best practices and the risks of injecting untrusted content. Employ web application firewalls (WAFs) with rules targeting known XSS patterns to provide an additional layer of defense. Finally, stay updated with vendor advisories and apply patches promptly once available.