CVE-2025-8567 in Nexter Blocks Plugin
Summary
by MITRE • 08/19/2025
The Nexter Blocks plugin for WordPress is vulnerable to Stored Cross-Site Scripting via multiple widgets in all versions up to, and including, 4.5.4 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 08/19/2025
The CVE-2025-8567 vulnerability affects the Nexter Blocks plugin for WordPress, representing a critical stored cross-site scripting weakness that has been present in all versions up to and including 4.5.4. This vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's widget implementation, creating a persistent security flaw that can be exploited by authenticated attackers possessing contributor-level privileges or higher. The vulnerability manifests through multiple widgets within the plugin's framework, making it particularly dangerous as it affects various user interface components that handle user-supplied data. The flaw allows malicious actors to inject arbitrary web scripts that will execute whenever any user accesses a page containing the injected content, creating a persistent threat vector that can compromise multiple users over time.
The technical nature of this vulnerability places it firmly within the CWE-79 category of Cross-Site Scripting, specifically classified as a stored XSS variant where malicious payloads are permanently stored on the server and executed when other users access affected pages. This weakness operates at the application layer and represents a significant escalation path for attackers who have already gained contributor-level access to a WordPress installation. The vulnerability's impact extends beyond simple script execution as it can be leveraged to steal user sessions, perform unauthorized actions on behalf of victims, or redirect users to malicious domains. The stored nature of the vulnerability means that the malicious code persists even after the initial injection, making it particularly difficult to detect and remediate compared to reflected XSS attacks.
From an operational perspective, this vulnerability creates a substantial risk for WordPress sites using the Nexter Blocks plugin, as it requires only contributor-level access to exploit effectively. This access level is often granted to users who should have limited privileges, making the attack vector more accessible than might be initially apparent. The impact affects all users who access pages containing the injected content, potentially compromising the entire user base of the affected website. Attackers can leverage this vulnerability to execute malicious scripts that may attempt to steal cookies, perform unauthorized administrative actions, or redirect users to phishing sites. The persistent nature of stored XSS means that victims may be compromised multiple times as long as they continue to access the affected pages, creating a sustained threat that can persist for extended periods without detection.
Organizations should immediately implement mitigations including updating to the latest version of the Nexter Blocks plugin where the vulnerability has been patched, applying the recommended security updates from the plugin developers, and conducting thorough security audits of all WordPress installations. The mitigation strategy should also include implementing proper input validation and output escaping mechanisms at the application level, as well as monitoring for suspicious activity in contributor accounts. Security teams should consider implementing web application firewalls to detect and block potential XSS payloads, while also establishing monitoring procedures to identify unauthorized content injection attempts. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other plugins or themes that may present similar risks. The ATT&CK framework categorizes this vulnerability under T1566 for credential access and T1059 for command and scripting interpreter, highlighting the potential for privilege escalation and persistent access that can be achieved through such stored XSS attacks.