CVE-2025-10166 is a stored Cross-Site Scripting (XSS) vulnerability found in the Social Media Shortcodes WordPress plugin developed by tw2113, specifically affecting the 'twitter' shortcode functionality in all versions up to and including 1.3.1. The vulnerability arises due to improper input sanitization and insufficient output escaping of user-supplied attributes within the shortcode implementation. Authenticated users with contributor-level permissions or higher can exploit this flaw by injecting malicious JavaScript code into pages or posts via the shortcode parameters. Because the injected script is stored persistently, it executes whenever any user accesses the compromised page, potentially leading to session hijacking, privilege escalation, or unauthorized actions performed on behalf of users viewing the page. The CVSS v3.1 base score is 6.4 (medium severity), reflecting that the attack vector is network-based, requires low attack complexity, but does require privileges (authenticated contributor or higher) and does not require user interaction for exploitation. The scope is changed, indicating that the vulnerability affects components beyond the initially vulnerable plugin, possibly impacting the entire WordPress site context. No known exploits have been reported in the wild yet, and no official patches have been linked at the time of publication. This vulnerability falls under CWE-79, which covers improper neutralization of input during web page generation, a common and critical web application security issue. Given WordPress's widespread use and the popularity of social media integration plugins, this vulnerability could be leveraged to compromise site visitors and administrators alike if exploited.

For European organizations using WordPress sites with the Social Media Shortcodes plugin, this vulnerability poses a significant risk to website integrity and user trust. Exploitation could lead to unauthorized script execution in the context of the affected website, enabling attackers to steal session cookies, deface content, or perform actions with the privileges of logged-in users. This is particularly concerning for organizations that rely on WordPress for public-facing websites, intranets, or customer portals, as it could lead to data leakage, reputational damage, and potential regulatory compliance issues under GDPR if personal data is exposed or manipulated. The requirement for contributor-level access means insider threats or compromised accounts could be leveraged to exploit this vulnerability. Additionally, the scope change suggests that the impact could extend beyond the plugin itself, potentially affecting other site components or plugins. While no active exploitation is currently known, the medium severity score and ease of exploitation (low complexity) warrant prompt attention to prevent future attacks. The vulnerability could also be used as a foothold for further attacks within an organization's web infrastructure.

European organizations should immediately audit their WordPress installations to identify the presence of the tw2113 Social Media Shortcodes plugin and verify its version. Until an official patch is released, organizations should consider the following mitigations: 1) Restrict contributor-level and higher permissions strictly to trusted users to reduce the risk of malicious shortcode injection. 2) Implement Web Application Firewall (WAF) rules to detect and block suspicious shortcode attribute patterns or script tags in post content. 3) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected sites. 4) Conduct manual code reviews or apply temporary input sanitization and output escaping patches if feasible. 5) Monitor site content for unexpected script injections or anomalies in pages using the twitter shortcode. 6) Educate content contributors about the risks of embedding untrusted code or attributes in shortcodes. 7) Regularly back up site content to enable quick restoration if compromise occurs. Once the vendor releases a security update, promptly apply the patch to fully remediate the vulnerability.