Executive Summary

This vulnerability is a Stored Cross-Site Scripting (XSS) issue in the Filr – Secure document library plugin for WordPress. It occurs because the plugin's file upload component (FILR_Uploader class) does not sufficiently restrict the types of files that can be uploaded. Specifically, authenticated users with Administrator-level access or higher can upload malicious HTML files containing JavaScript. When other users with permission to create or edit 'filr' post types access these uploaded files, the malicious JavaScript executes, potentially compromising their security. [2, 4]

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Impact Analysis

This vulnerability can allow attackers with administrator-level access to upload malicious HTML files that execute JavaScript in the context of users who view or edit the affected 'filr' post types. This can lead to unauthorized actions such as stealing user credentials, session hijacking, or performing actions on behalf of other users. The CVSS score indicates a moderate impact with potential confidentiality and integrity loss but no availability impact.

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Detection Guidance

Detection of this vulnerability involves checking for the presence of the vulnerable Filr plugin versions (up to and including 1.2.11) on your WordPress installation and monitoring for suspicious file uploads, especially HTML files containing JavaScript uploaded by users with Administrator-level access or higher. Since the vulnerability is a Stored Cross-Site Scripting via unrestricted file upload, you can look for uploaded files with disallowed extensions (like .html) in the upload directories related to the 'filr' post type. Commands to detect suspicious files could include scanning the upload directories for unexpected file types or recently modified files. For example, on a Linux server hosting WordPress, you might run commands like: 1. Find recently uploaded HTML files: ```bash find /path/to/wordpress/wp-content/uploads/ -type f -name '*.html' -mtime -7 ``` 2. Search for files containing suspicious JavaScript: ```bash grep -ril '<script' /path/to/wordpress/wp-content/uploads/ ``` 3. Check plugin version installed: ```bash wp plugin get filr-protection --field=version ``` These commands help identify potentially malicious uploaded files and verify if the vulnerable plugin version is in use. Additionally, monitoring logs for file upload activities by administrator users may help detect exploitation attempts. [2, 4]

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Mitigation Strategies

Immediate mitigation steps include upgrading the Filr plugin to version 1.2.12 or later, where the vulnerability is addressed by implementing strict file type restrictions and validation in the FILR_Uploader class. Until the upgrade can be applied, restrict Administrator-level users from uploading files via the Filr plugin or disable the plugin entirely to prevent exploitation. Additionally, review and tighten file upload permissions and monitor uploaded files for suspicious content. Implementing web application firewall (WAF) rules to block malicious file uploads and scanning existing uploads for malicious HTML or JavaScript files can also help mitigate risk. [2, 4, 3]

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