CVE-2025-5539 is a stored Cross-Site Scripting (XSS) vulnerability affecting the Simple Contact Form Plugin for WordPress – WP Easy Contact, developed by emarket-design. This vulnerability exists in all versions up to and including 4.0.0 due to improper input sanitization and insufficient output escaping of user-supplied attributes within the plugin's 'emd_mb_meta' shortcode. Specifically, authenticated users with contributor-level privileges or higher can inject arbitrary JavaScript code into pages generated by the plugin. Because the malicious script is stored persistently, it executes every time any user accesses the compromised page, potentially leading to session hijacking, defacement, or other malicious actions. The vulnerability is classified under CWE-79, indicating improper neutralization of input during web page generation. The CVSS v3.1 base score is 6.4 (medium severity), reflecting network exploitability with low attack complexity, requiring privileges but no user interaction, and impacting confidentiality and integrity with a scope change. No known exploits are currently reported in the wild, but the vulnerability's nature and ease of exploitation by authenticated users make it a significant risk for WordPress sites using this plugin. The lack of available patches at the time of publication increases exposure for affected installations.

For European organizations, this vulnerability poses a moderate risk primarily to websites running WordPress with the vulnerable WP Easy Contact plugin installed. Exploitation could lead to unauthorized script execution, enabling attackers to steal session cookies, perform actions on behalf of legitimate users, or deliver malware payloads. This can compromise user data confidentiality and website integrity, potentially damaging organizational reputation and violating data protection regulations such as GDPR. Since contributor-level access is required, insider threats or compromised accounts could be leveraged to exploit this flaw. The persistent nature of stored XSS increases the risk of widespread impact across site visitors and administrators. Organizations relying on WordPress for customer interaction or internal communication should be particularly cautious, as the plugin is designed for contact forms, a common feature on corporate websites. The vulnerability may also facilitate further attacks, such as privilege escalation or phishing campaigns, amplifying its impact.

European organizations should immediately audit their WordPress installations to identify the presence of the WP Easy Contact plugin and verify its version. Until an official patch is released, consider disabling or removing the plugin to eliminate exposure. Restrict contributor-level permissions strictly and monitor accounts with such privileges for suspicious activity. Implement Web Application Firewalls (WAFs) with rules to detect and block typical XSS payloads targeting the 'emd_mb_meta' shortcode parameters. Employ Content Security Policy (CSP) headers to limit script execution sources, mitigating the impact of injected scripts. Regularly review and sanitize user inputs on all forms and shortcodes, and apply output encoding best practices. Additionally, maintain up-to-date backups and monitor website integrity to quickly detect and recover from any compromise. Once a patch becomes available, prioritize prompt application and test in staging environments before deployment.