CVE-2025-11857 is a stored Cross-Site Scripting (XSS) vulnerability identified in the XX2WP Integration Tools plugin for WordPress, specifically affecting all versions up to and including 1.9.9. The vulnerability stems from improper neutralization of input during web page generation (CWE-79), where the plugin fails to properly sanitize the 'post_id' parameter used in the 'mxp_fb2wp_display_embed' shortcode. This flaw allows authenticated users with contributor-level access or higher to inject arbitrary JavaScript code into WordPress pages. Because the malicious script is stored, it executes every time a user accesses the infected page, potentially compromising user sessions, stealing cookies, or performing unauthorized actions on behalf of users. The vulnerability has a CVSS 3.1 base score of 6.4, indicating medium severity, with an attack vector of network (remote), low attack complexity, requiring privileges (PR:L), no user interaction, and scope change (S:C). The impact affects confidentiality and integrity but not availability. No patches or known exploits are currently reported, but the risk remains significant due to the ease of exploitation by contributors. The vulnerability highlights the importance of input validation and output encoding in WordPress plugins, especially those that handle user-generated content or parameters. Organizations using this plugin should monitor for updates and consider temporary mitigations such as limiting contributor privileges or disabling the shortcode until fixed.

For European organizations, this vulnerability poses a risk primarily to websites and intranet portals running WordPress with the XX2WP Integration Tools plugin installed. The ability for contributors to inject persistent malicious scripts can lead to session hijacking, unauthorized data access, defacement, or distribution of malware to site visitors. This can damage organizational reputation, lead to data breaches involving personal or sensitive information, and cause compliance issues under GDPR due to unauthorized data exposure. Since contributors typically have limited privileges, the attack surface is somewhat constrained, but insider threats or compromised contributor accounts increase risk. The scope change in the CVSS vector indicates that the vulnerability can affect resources beyond the initially compromised component, potentially impacting other users or integrated systems. The lack of known exploits in the wild reduces immediate risk but does not eliminate it, especially as attackers often reverse-engineer disclosed vulnerabilities. Organizations with multiple content contributors or public-facing WordPress sites are particularly vulnerable. The impact on availability is minimal, but confidentiality and integrity impacts are moderate, warranting timely mitigation.

1. Monitor the vendor’s official channels for patches or updates addressing CVE-2025-11857 and apply them immediately upon release. 2. Until a patch is available, restrict contributor-level access to trusted users only, minimizing the risk of malicious script injection. 3. Disable or remove the 'mxp_fb2wp_display_embed' shortcode functionality if feasible, to prevent exploitation via the vulnerable parameter. 4. Implement Web Application Firewall (WAF) rules to detect and block suspicious input patterns targeting the 'post_id' parameter. 5. Conduct regular security audits and code reviews of WordPress plugins, focusing on input validation and output encoding practices. 6. Educate contributors about the risks of injecting untrusted content and enforce strict content submission policies. 7. Employ Content Security Policy (CSP) headers to limit the impact of potential XSS by restricting script sources. 8. Monitor logs for unusual activity related to shortcode usage or contributor actions. 9. Consider using security plugins that can detect and block XSS attempts or sanitize inputs at runtime. 10. Backup WordPress sites regularly to enable quick restoration if exploitation occurs.