CVE-2025-3583 in Newsletter Plugin
Summary
by MITRE • 05/05/2025
The Newsletter WordPress plugin before 8.7.1 does not sanitise and escape some of its 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 • 05/05/2025
The vulnerability identified as CVE-2025-3583 affects the Newsletter WordPress plugin version 8.7.1 and earlier, presenting a significant security risk through stored cross-site scripting flaws. This issue specifically targets high-privilege users such as administrators who possess the capability to modify plugin settings despite restrictions on unfiltered_html permissions. The vulnerability stems from inadequate sanitization and escaping mechanisms within the plugin's configuration handling processes, creating an attack vector that could be exploited even in environments where strict content filtering is enforced.
The technical flaw manifests when administrators interact with the plugin's settings interface, particularly in multisite WordPress installations where the unfiltered_html capability may be explicitly restricted. The plugin fails to properly sanitize user inputs before storing them in the database, allowing malicious scripts to be injected into configuration fields. These stored scripts then execute whenever the affected settings are rendered in the admin interface or displayed on frontend pages, creating a persistent XSS vulnerability that can affect other users who view the compromised content. The vulnerability is classified under CWE-79 as a failure to sanitize user input, specifically manifesting as stored cross-site scripting.
The operational impact of this vulnerability extends beyond simple script execution, as it enables attackers with administrator privileges to perform various malicious activities including session hijacking, data exfiltration, and privilege escalation within the WordPress environment. In a multisite setup where unfiltered_html is disabled for security reasons, the vulnerability becomes particularly dangerous as it circumvents the intended protection mechanisms. Attackers could potentially inject scripts that redirect users to malicious sites, steal cookies, or modify content in ways that compromise the entire network of interconnected sites. The vulnerability also undermines the principle of least privilege by allowing authenticated users to execute code that could affect the broader WordPress installation.
Mitigation strategies for CVE-2025-3583 should prioritize immediate plugin updates to version 8.7.1 or later, which includes proper sanitization and escaping mechanisms for all user-controllable settings. Organizations should conduct thorough security audits of their WordPress installations to identify any other plugins or themes that may exhibit similar sanitization flaws. System administrators should review and tighten access controls, ensuring that only essential personnel maintain administrator privileges. The implementation of web application firewalls and content security policies can provide additional defense-in-depth measures, while regular security monitoring should be established to detect potential exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1566.001 for spearphishing attachment, as it enables attackers to execute malicious code through compromised administrative accounts and potentially deliver payloads through crafted newsletter content.