CVE-2019-25138 in User Submitted Posts Plugin
Summary
by MITRE • 06/07/2023
The User Submitted Posts plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the usp_check_images function in versions up to, and including, 20190312. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected sites server which may make remote code execution possible.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/09/2026
The vulnerability identified as CVE-2019-25138 affects the User Submitted Posts plugin for WordPress, a widely used component that allows visitors to submit content to websites. This particular flaw exists within the usp_check_images function where the plugin fails to properly validate file types during the upload process. The issue impacts all versions up to and including 20190312, making it a significant concern for WordPress administrators who have not updated their installations. The vulnerability stems from inadequate input validation mechanisms that should have prevented malicious file uploads but were instead bypassed by attackers.
The technical exploitation of this vulnerability occurs through the absence of proper file type validation in the usp_check_images function, which represents a clear violation of security best practices. This flaw falls under CWE-434, which specifically addresses "Unrestricted Upload of File with Dangerous Type," indicating that the plugin does not properly restrict file uploads to only safe file types such as images. Attackers can leverage this weakness to upload malicious files including php scripts, which when executed on the web server could provide full control over the affected WordPress installation. The vulnerability is particularly dangerous because it affects unauthenticated users, meaning anyone with access to the website can exploit it without requiring valid credentials.
The operational impact of this vulnerability extends beyond simple file uploads and presents a severe risk for remote code execution capabilities. When attackers successfully upload malicious files, they can execute arbitrary code on the affected server, potentially leading to complete system compromise. This vulnerability directly aligns with ATT&CK technique T1190, "Exploit Public-Facing Application," as it represents an attack against a publicly accessible web application component. The consequences include potential data breaches, website defacement, server takeover, and the ability to use compromised systems as launching points for further attacks within the network. Organizations running vulnerable WordPress installations face significant exposure to these threats, particularly those with limited security monitoring and patch management processes.
Mitigation strategies for CVE-2019-25138 require immediate action including updating to the latest version of the User Submitted Posts plugin where the file validation issues have been addressed. Administrators should also implement additional security measures such as restricting file upload capabilities to only trusted users, implementing proper file type validation at multiple layers, and deploying web application firewalls to detect and block malicious upload attempts. The vulnerability demonstrates the critical importance of proper input validation and the principle of least privilege in web application security. Security teams should also conduct comprehensive vulnerability assessments of all WordPress plugins and themes to identify similar issues, as this vulnerability represents a common pattern in web application security flaws that can be prevented through proper security development practices and regular security updates.