CVE-2018-6015 in Email Subscribers
Summary
by MITRE
An issue was discovered in the "Email Subscribers & Newsletters" plugin before 3.4.8 for WordPress. Sending an HTTP POST request to a URI with /?es=export at the end, and adding option=view_all_subscribers in the body, allows downloading of a CSV data file with all subscriber data.
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Analysis
by VulDB Data Team • 12/29/2019
The vulnerability identified as CVE-2018-6015 affects the Email Subscribers & Newsletters WordPress plugin, specifically versions prior to 3.4.8, presenting a critical access control flaw that enables unauthorized data exfiltration. This issue stems from insufficient authentication checks within the plugin's export functionality, creating a path for malicious actors to bypass normal access restrictions and obtain sensitive subscriber information. The vulnerability manifests when an attacker sends a specially crafted HTTP POST request to a specific URI endpoint containing the parameter /?es=export followed by a body parameter option=view_all_subscribers, which triggers the plugin to generate and serve a CSV file containing all subscriber data without proper authorization verification.
The technical exploitation of this vulnerability involves a classic privilege escalation scenario where the plugin fails to validate user permissions before executing sensitive operations. The flaw resides in the plugin's handling of the export functionality, where the view_all_subscribers option parameter is processed without adequate authentication checks, allowing any remote attacker to access subscriber data that should be restricted to authorized administrators. This represents a clear violation of the principle of least privilege and demonstrates poor input validation practices within the plugin's codebase. The vulnerability can be categorized under CWE-284, which addresses improper access control mechanisms, and aligns with ATT&CK technique T1213.002 for data from information repositories, as it enables extraction of sensitive data from a web application's database.
The operational impact of this vulnerability is severe, as it allows complete exposure of all subscriber information including email addresses and potentially associated personal details, depending on the plugin's configuration. Organizations using affected versions of the plugin face significant risk of data breaches, potential regulatory violations under GDPR and other data protection frameworks, and possible reputational damage from unauthorized disclosure of user information. The vulnerability creates a persistent risk since it does not require authentication credentials to exploit, making it particularly dangerous in environments where the plugin is deployed without additional network-level access controls or monitoring. Attackers can leverage this vulnerability to build comprehensive subscriber databases for spam campaigns, identity theft attempts, or other malicious activities, while the lack of audit logging for this specific export operation makes detection challenging for security teams.
Mitigation strategies for CVE-2018-6015 primarily involve immediate upgrade to plugin version 3.4.8 or later, which contains the necessary authentication checks and access control improvements. Organizations should also implement network-level restrictions to limit access to plugin endpoints, particularly those handling export functionality, and deploy web application firewalls to monitor and block suspicious requests targeting the vulnerable URI patterns. Security monitoring should include logging and alerting for unusual export operations, and regular security audits should verify that no unauthorized access points exist within the WordPress installation. Additionally, implementing role-based access controls and ensuring that only authorized administrators have access to plugin management functions will reduce the attack surface and limit potential damage from similar vulnerabilities in the future. The remediation process should also include verifying that all plugin installations are kept current with security updates and establishing automated patch management processes to prevent similar issues from arising in other components of the web application stack.