CVE-2025-9762 in Post by Email Plugin
Summary
by MITRE • 09/30/2025
The Post By Email plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the save_attachments function in all versions up to, and including, 1.0.4b. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible.
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Analysis
by VulDB Data Team • 09/30/2025
The Post By Email plugin for WordPress presents a critical security vulnerability classified as CVE-2025-9762 that stems from inadequate input validation mechanisms within its file handling processes. This vulnerability exists in all versions up to and including 1.0.4b, creating a significant attack surface for malicious actors who seek to compromise WordPress installations. The flaw specifically resides in the save_attachments function where the plugin fails to properly validate file types during the upload process, allowing attackers to bypass intended security restrictions.
The technical implementation of this vulnerability demonstrates a classic path traversal and arbitrary file upload flaw that aligns with CWE-434, which describes insecure file upload vulnerabilities where applications fail to validate or restrict file types. The missing validation occurs at the application layer where the plugin accepts email attachments without proper sanitization of file extensions or content verification. This weakness enables attackers to upload malicious files such as php shells, web shells, or other executable code that can be executed on the target server.
From an operational perspective, this vulnerability creates a severe risk landscape for WordPress administrators and site owners who rely on the Post By Email plugin for automated content creation. The impact extends beyond simple file corruption as the vulnerability allows for potential remote code execution, which can lead to complete system compromise. Attackers can leverage this flaw to establish persistent backdoors, exfiltrate sensitive data, or use the compromised server as a launchpad for further attacks within the network. The unauthenticated nature of this vulnerability means that any user with access to the email endpoint can exploit this weakness without requiring prior credentials or elevated privileges.
The attack vector for this vulnerability typically involves sending specially crafted email messages containing malicious attachments to the plugin's email endpoint. Once received, the plugin processes these attachments without proper validation, storing them in the WordPress upload directory where they can be accessed through standard web requests. This creates a persistent threat where attackers can upload files that remain undetected for extended periods, potentially allowing for long-term compromise of the affected system. The vulnerability's exploitation aligns with ATT&CK technique T1105 which describes the use of file transfer methods to establish persistence on compromised systems.
Organizations should immediately implement mitigations including upgrading to the latest version of the Post By Email plugin where this vulnerability has been addressed, implementing additional file validation mechanisms at the web server level, and monitoring upload directories for suspicious file activity. Network-based solutions such as web application firewalls can provide additional protection by filtering out requests containing potentially malicious file types. Administrators should also consider implementing strict file type whitelisting policies and conducting regular security audits of plugin installations to ensure no vulnerable components remain in production environments. The vulnerability underscores the importance of maintaining up-to-date software and implementing defense-in-depth strategies to protect against similar weaknesses in other components of the WordPress ecosystem.