CVE-2026-4882 in User Registration Advanced Fields Plugin
Summary
by MITRE • 05/02/2026
The User Registration Advanced Fields plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the 'URAF_AJAX::method_upload' function in all versions up to, and including, 1.6.20. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible. Note: The vulnerability can only be exploited if a "Profile Picture" field is added to the form.
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Analysis
by VulDB Data Team • 05/25/2026
The User Registration Advanced Fields plugin for WordPress presents a critical security vulnerability through its insufficient input validation mechanisms within the URAF_AJAX::method_upload function. This flaw exists in all plugin versions up to and including 1.6.20, creating a pathway for unauthenticated attackers to bypass security controls and upload malicious files to the target server. The vulnerability specifically targets the file upload functionality that is typically used for profile picture fields, making it particularly dangerous as it leverages legitimate user interaction points to execute malicious operations. The absence of proper file type validation allows attackers to upload files with potentially harmful extensions that could compromise the entire WordPress installation.
The technical nature of this vulnerability stems from the lack of proper file validation checks within the plugin's AJAX upload handler. When users interact with the profile picture field, the plugin accepts file uploads without verifying the file type, content, or extension against a whitelist of acceptable formats. This missing validation creates a direct attack vector where malicious actors can upload files with extensions such as .php, .jsp, or other server-side scripting languages that could execute code on the web server. The vulnerability operates at the application layer and directly impacts the integrity and confidentiality of the WordPress environment, as it allows attackers to establish persistent access points through uploaded malicious payloads.
The operational impact of this vulnerability extends beyond simple file uploads, as it creates opportunities for remote code execution and potential system compromise. Attackers who exploit this vulnerability can upload web shells or other malicious scripts that provide them with persistent access to the compromised WordPress installation. The vulnerability's conditionality, requiring a "Profile Picture" field to be present in the form, does not reduce its severity as it only requires the attacker to identify and target a vulnerable installation with this specific field configuration. This makes the vulnerability particularly dangerous in environments where user registration forms are publicly accessible and widely used.
Security professionals should note this vulnerability's alignment with CWE-434, which addresses the improper restriction of uploads of executable files, and its mapping to ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications. The recommended mitigations include immediate plugin updates to versions that address the validation issue, implementation of additional file type restrictions at the web server level, and configuration of proper file upload directory permissions to prevent execution of uploaded files. Organizations should also consider implementing web application firewalls and monitoring for suspicious file upload activities to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of input validation and proper security controls in plugin development, particularly for features that handle user-generated content and file uploads.