CVE-2021-24736 in Shared Files Plugin
Summary
by MITRE • 10/18/2021
The Easy Download Manager and File Sharing Plugin with frontend file upload – a better Media Library — Shared Files WordPress plugin before 1.6.57 does not sanitise and escape some of its settings before outputting them in attributes, which could lead to Stored Cross-Site Scripting issues.
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Analysis
by VulDB Data Team • 10/22/2021
The vulnerability identified as CVE-2021-24736 affects the Easy Download Manager and File Sharing Plugin with frontend file upload - a better Media Library - Shared Files WordPress plugin version 1.6.57 and earlier. This security flaw represents a critical stored cross-site scripting vulnerability that arises from insufficient sanitization and escaping of user-controllable data within the plugin's settings. The vulnerability specifically impacts how the plugin handles data when rendering attributes in web pages, creating an avenue for malicious actors to inject persistent malicious scripts into the plugin's administrative interfaces and frontend displays.
The technical root cause of this vulnerability stems from the plugin's failure to properly sanitize user input before incorporating it into HTML attributes. According to CWE-79, this constitutes a classic stored cross-site scripting vulnerability where malicious scripts are stored on the server and executed when other users view affected pages. The flaw occurs in the plugin's handling of settings data that gets output directly into HTML attributes without proper escaping mechanisms, allowing attackers to inject malicious JavaScript code that persists across user sessions. This vulnerability falls under the ATT&CK technique T1566.001 which involves the exploitation of web application vulnerabilities to execute malicious code.
The operational impact of this vulnerability is severe as it enables attackers to execute arbitrary JavaScript code in the context of any user's browser who interacts with the affected WordPress site. An attacker who gains access to the plugin's administrative settings could inject malicious scripts that could steal user sessions, perform unauthorized actions on behalf of users, or redirect them to malicious sites. The stored nature of the vulnerability means that the malicious code persists even after the initial injection, making it particularly dangerous as it affects all users who encounter the compromised content. This vulnerability could be exploited by attackers with minimal privileges if they can modify plugin settings, potentially leading to full site compromise.
Mitigation strategies for CVE-2021-24736 should prioritize immediate patching of the plugin to version 1.6.57 or later, which contains the necessary sanitization and escaping fixes. Administrators should also implement proper input validation and output escaping mechanisms throughout the plugin's codebase, ensuring that all user-controllable data is properly sanitized before being rendered in HTML attributes. Network monitoring should be enhanced to detect unusual patterns in plugin settings modifications, and regular security audits should be conducted to identify similar vulnerabilities in other installed plugins. Additionally, implementing web application firewalls and content security policies can provide additional layers of protection against exploitation attempts. The vulnerability demonstrates the critical importance of proper data sanitization practices in web applications and serves as a reminder of the potential consequences when input validation and output escaping mechanisms are inadequate.