CVE-2023-1844 in Subscribe2 Plugin
Summary
by MITRE • 06/28/2023
The Subscribe2 plugin for WordPress is vulnerable to unauthorized access to email functionality due to a missing capability check when sending test emails in versions up to, and including, 10.40. This makes it possible for author-level attackers to send emails with arbitrary content and attachments to site users.
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Analysis
by VulDB Data Team • 04/10/2026
The CVE-2023-1844 vulnerability resides within the Subscribe2 plugin for WordPress, a widely used email subscription management tool that allows website administrators to collect user email addresses and send newsletters or updates. This particular flaw represents a critical authorization bypass issue that undermines the plugin's security model. The vulnerability specifically affects versions up to and including 10.40, indicating a persistent flaw that has remained unaddressed for an extended period within the plugin's development lifecycle. The core issue stems from the absence of proper capability checks during the test email sending process, which fundamentally compromises the plugin's access control mechanisms.
The technical exploitation of this vulnerability occurs when an attacker with author-level privileges attempts to send test emails through the Subscribe2 plugin interface. Without adequate capability verification, the plugin fails to validate whether the requesting user possesses sufficient permissions to perform email operations. This missing validation creates an unauthorized access vector where authors can leverage the plugin's email functionality to send arbitrary content and attachments to registered site users. The flaw essentially allows privilege escalation within the context of the plugin's email delivery system, transforming a limited author role into a potential vector for spam distribution or malicious content delivery.
The operational impact of CVE-2023-1844 extends beyond simple unauthorized email sending capabilities. Attackers can exploit this vulnerability to conduct phishing campaigns, distribute malware through email attachments, or send spam content that could damage the website's reputation and user trust. The ability to include arbitrary attachments makes this particularly dangerous as it enables attackers to deliver malicious files directly to users' inboxes. Additionally, the vulnerability could be used for social engineering attacks where attackers craft convincing email content to manipulate users into performing actions that benefit the attacker. The compromised email functionality may also be used to generate false notifications or alerts that could mislead users about the website's status or security posture.
This vulnerability aligns with CWE-284, which addresses improper access control issues in software systems. The missing capability check directly violates the principle of least privilege by allowing users with minimal permissions to access functionality reserved for higher-privileged roles. From an attack perspective, this flaw maps to several ATT&CK techniques including TA0001 (Initial Access) through the use of compromised author accounts and TA0005 (Defense Evasion) by leveraging legitimate plugin functionality to avoid detection. The vulnerability also intersects with TA0003 (Persistence) as attackers might establish ongoing access through email-based reconnaissance or communication channels. Organizations should prioritize immediate patching of affected versions while implementing network monitoring to detect unusual email traffic patterns that might indicate exploitation attempts.
Mitigation strategies should include immediate updates to the Subscribe2 plugin to versions that address the capability check vulnerability, along with comprehensive review of user roles and permissions within WordPress installations. Administrators should implement additional email filtering and monitoring systems to detect suspicious email patterns and unauthorized sending activities. Regular security audits of WordPress plugins and themes should be conducted to identify similar authorization bypass vulnerabilities. The incident highlights the critical importance of capability validation in web applications and underscores the need for security-by-design principles in plugin development. Organizations should also consider implementing role-based access controls that limit the scope of author-level privileges, particularly for plugins that handle sensitive functionality like email delivery and user communication.