CVE-2025-5754 is a stored Cross-Site Scripting (XSS) vulnerability affecting the WordPress plugin 'Useful Tab Block – Responsive & AMP-Compatible' developed by bbc000tommy. This vulnerability exists in all versions up to and including 1.3.2 due to improper neutralization of input during web page generation, specifically via the 'className' parameter. The root cause is insufficient input sanitization and output escaping, allowing an attacker with authenticated Contributor-level access or higher to inject arbitrary JavaScript code into pages. When other users access these compromised pages, the injected scripts execute in their browsers, potentially leading to session hijacking, privilege escalation, defacement, or redirection to malicious sites. The vulnerability has a CVSS 3.1 base score of 6.4, indicating a medium severity level. It requires network access (remote), low attack complexity, and privileges at the Contributor level, but no user interaction is needed for exploitation. The scope is changed, meaning the vulnerability can affect resources beyond the initially compromised component, such as other users viewing the injected content. No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability is categorized under CWE-79, which covers improper neutralization of input leading to XSS attacks. Stored XSS is particularly dangerous because the malicious payload persists on the server and affects multiple users over time, increasing the attack surface and potential impact.

For European organizations using WordPress websites with the 'Useful Tab Block – Responsive & AMP-Compatible' plugin, this vulnerability poses a significant risk to website integrity and user trust. Attackers with Contributor-level access—which may be granted to content editors or other non-administrative roles—can inject malicious scripts that execute in the browsers of site visitors, including employees, customers, or partners. This can lead to theft of authentication cookies, enabling session hijacking and unauthorized access to user accounts. It can also facilitate phishing attacks by redirecting users to malicious domains or displaying fraudulent content. The compromise of website content can damage brand reputation and lead to regulatory scrutiny under GDPR if personal data is exposed or manipulated. Additionally, the vulnerability could be leveraged as a foothold for further attacks within the organization's network if internal users are targeted. Given the widespread use of WordPress in Europe and the popularity of responsive and AMP-compatible plugins to optimize mobile user experience, the potential impact on confidentiality and integrity is considerable, although availability is not directly affected.

European organizations should immediately audit their WordPress installations to identify the presence of the 'Useful Tab Block – Responsive & AMP-Compatible' plugin and verify its version. Until an official patch is released, the following specific mitigations are recommended: 1) Restrict Contributor-level permissions strictly to trusted users and review user roles to minimize unnecessary privileges. 2) Implement Web Application Firewalls (WAFs) with custom rules to detect and block suspicious payloads targeting the 'className' parameter. 3) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts and reduce the impact of XSS attacks. 4) Conduct regular security scans focusing on stored XSS indicators within site content. 5) Educate content editors about the risks of injecting untrusted input and enforce strict input validation policies. 6) Monitor website logs for unusual activity related to content changes or script injections. 7) Consider temporarily disabling or removing the vulnerable plugin if feasible until a patch is available. 8) Stay updated with vendor advisories and apply patches promptly once released.