CVE-2021-4367 in Easy Drag & Drop Form Builder Plugin
Summary
by MITRE • 06/07/2023
The Flo Forms – Easy Drag & Drop Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Options Change by using the flo_import_forms_options AJAX action in versions up to, and including, 1.0.35 due to insufficient input sanitization and output escaping along with missing capability checks. This makes it possible for authenticated attackers, like subscribers, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
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Analysis
by VulDB Data Team • 07/05/2023
The Flo Forms plugin for WordPress represents a popular drag-and-drop form builder solution that has been identified with a critical stored cross-site scripting vulnerability in versions up to and including 1.0.35. This vulnerability stems from inadequate input sanitization and output escaping mechanisms within the plugin's codebase, specifically affecting the flo_import_forms_options AJAX action endpoint. The flaw allows authenticated attackers with minimal privileges to execute malicious scripts within the context of other users' browsers, creating a significant security risk for WordPress installations that rely on this plugin. The vulnerability's impact extends beyond simple script execution as it provides a persistent attack vector that can compromise user sessions and potentially lead to further exploitation within the WordPress environment.
The technical implementation of this vulnerability involves the plugin's failure to properly validate and sanitize user input received through the AJAX interface, combined with insufficient capability checks that allow unauthorized users to access restricted administrative functions. When an authenticated user with subscriber privileges manipulates the flo_import_forms_options endpoint, the plugin processes the input without adequate sanitization measures, resulting in stored XSS conditions. This weakness aligns with CWE-79, which specifically addresses cross-site scripting vulnerabilities, and demonstrates how insufficient input validation can lead to persistent security flaws in web applications. The vulnerability operates at the application layer and requires authentication to exploit, making it particularly dangerous as it can be leveraged by insiders or compromised accounts.
The operational impact of this vulnerability extends far beyond simple script injection, as it provides attackers with the ability to manipulate user sessions, steal cookies, redirect users to malicious sites, and potentially escalate privileges within the WordPress environment. An attacker could craft malicious form options that, when processed by the plugin, would execute scripts in the browsers of other users who access pages containing these injected elements. This persistent nature of stored XSS makes the vulnerability particularly dangerous for WordPress sites where multiple users interact with the platform, as the attack can affect any user who encounters the malicious content. The vulnerability also aligns with ATT&CK technique T1546.001, which covers modifications to Windows Registry or other system-level configurations, as the compromised forms could be used to establish persistent access patterns.
Mitigation strategies for this vulnerability require immediate attention through plugin updates to versions that address the input sanitization and capability check deficiencies. System administrators should implement strict input validation mechanisms and ensure that all user-supplied data is properly escaped before being stored or rendered in web pages. The WordPress security community recommends that all plugins undergo thorough security audits to prevent similar issues, particularly focusing on AJAX endpoints and user privilege management. Additionally, implementing web application firewalls and monitoring for suspicious AJAX requests can help detect and prevent exploitation attempts. Organizations should also consider implementing role-based access controls that limit the capabilities of lower-privileged users and establish regular security assessments of third-party plugins to prevent similar vulnerabilities from being introduced into their WordPress environments.