CVE-2025-3582 in Newsletter Plugin
Summary
by MITRE • 06/09/2025
The Newsletter WordPress plugin before 8.85 does not sanitise and escape some of its Form settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
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Analysis
by VulDB Data Team • 06/09/2025
The vulnerability identified as CVE-2025-3582 affects the Newsletter WordPress plugin version 8.84 and earlier, presenting a critical security risk through stored cross-site scripting flaws in its form settings management. This issue specifically targets high-privilege users such as administrators who possess the capability to modify plugin configurations despite restrictions on unfiltered_html capabilities. The vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's form handling components, creating an attack vector that bypasses standard WordPress security measures designed to prevent malicious script execution in content areas.
The technical flaw manifests in the plugin's failure to properly sanitize user inputs when processing form settings, particularly within administrative interfaces where administrators configure newsletter subscription forms. When high-privilege users modify these settings, malicious scripts can be injected and stored within the plugin's configuration data structures. These stored scripts then execute whenever the form settings are rendered or processed, potentially affecting other users who access the administrative interface or view pages containing the compromised form elements. The vulnerability is particularly concerning in multisite WordPress installations where the unfiltered_html capability may be restricted for security reasons, yet the flaw allows bypassing these protections through the plugin's form handling mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to perform session hijacking, defacement of administrative interfaces, data exfiltration, or further privilege escalation within the WordPress environment. Since the vulnerability affects administrators in multisite setups where unfiltered_html is typically restricted, it represents a significant bypass of WordPress security models designed to prevent malicious code injection in restricted user contexts. Attackers could leverage this flaw to compromise entire WordPress networks by targeting a single vulnerable plugin installation, especially when administrators are unaware of the specific security implications of modifying form settings.
Mitigation strategies should prioritize immediate plugin updates to version 8.85 or later, which contain the necessary sanitization and escaping fixes for the affected form settings. Administrators should also implement additional security measures including regular security audits of plugin configurations, monitoring of administrative interfaces for unauthorized modifications, and implementation of web application firewalls to detect and block suspicious script injection attempts. The vulnerability aligns with CWE-79 (Cross-Site Scripting) and maps to ATT&CK technique T1548.001 (Abuse Elevation Control Mechanism) through the bypass of WordPress security controls. Organizations should also consider restricting administrative privileges to only essential personnel and implementing least-privilege access controls for plugin management functions to minimize potential impact from such vulnerabilities.