CVE-2026-2343: Ultimate Invoice Plugin Info Disclosure

CVE-2026-2343 Overview

The PeproDev Ultimate Invoice WordPress plugin through version 2.2.5 contains an information disclosure vulnerability in its bulk download invoices functionality. The plugin generates ZIP archives containing exported invoice PDFs with predictable filenames, allowing unauthenticated attackers to brute force and retrieve sensitive personally identifiable information (PII) from invoice documents.

Critical Impact

Unauthenticated attackers can retrieve invoice ZIP archives containing customer PII by exploiting predictable filename patterns in the bulk download feature.

Affected Products

• PeproDev Ultimate Invoice WordPress plugin through version 2.2.5
• WordPress installations using the vulnerable plugin versions
• Sites with bulk invoice export functionality enabled

Discovery Timeline

• 2026-03-25 - CVE-2026-2343 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-2343

Vulnerability Analysis

This vulnerability stems from insecure design in the invoice export functionality. When administrators use the bulk download feature to export invoices as PDFs, the plugin packages them into ZIP archives. These archives are stored in a web-accessible location with filenames that follow a predictable naming convention.

The predictable nature of the ZIP filenames enables attackers to enumerate and download archive files without authentication. Invoice documents typically contain sensitive customer information including names, addresses, email addresses, phone numbers, and purchase details. This represents a significant privacy violation and potential compliance issue under regulations such as GDPR.

The attack can be performed remotely over the network without requiring any user interaction or authentication, making it trivially exploitable. While the vulnerability does not allow modification or deletion of data, the confidentiality breach can have serious consequences for affected customers and the organization.

Root Cause

The root cause is the use of predictable or sequential naming patterns for generated ZIP archive files combined with inadequate access controls. The plugin fails to implement proper randomization in filename generation and does not restrict access to the download directory, allowing any unauthenticated user to request and retrieve the exported invoice archives.

Attack Vector

The attack is network-based and can be executed by any remote attacker. The exploitation flow involves:

1. Identifying the target WordPress site using the PeproDev Ultimate Invoice plugin
2. Discovering the download endpoint or directory where ZIP files are stored
3. Brute forcing the predictable filename pattern to enumerate available archives
4. Downloading the ZIP files containing invoice PDFs with customer PII

The vulnerability requires no privileges or user interaction to exploit. An attacker simply needs to understand the filename pattern and systematically request potential filenames until valid archives are discovered.

Detection Methods for CVE-2026-2343

Indicators of Compromise

• Unusual volume of HTTP requests to the plugin's download directory
• Sequential or patterned requests for ZIP files from single IP addresses
• Access log entries showing enumeration attempts against invoice archive endpoints
• Successful downloads of ZIP files by unauthorized or external IP addresses

Detection Strategies

• Monitor web server access logs for brute force patterns targeting ZIP file downloads
• Implement rate limiting on endpoints serving downloadable content
• Configure Web Application Firewall (WAF) rules to detect enumeration attempts
• Set up alerts for high-volume requests to the plugin's export functionality

Monitoring Recommendations

• Enable detailed logging for the WordPress uploads directory
• Monitor for unusual patterns in HTTP 200 responses for ZIP file requests
• Track access to invoice-related endpoints by IP address and frequency
• Review authentication logs for attempts to access administrative plugin functions

How to Mitigate CVE-2026-2343

Immediate Actions Required

• Update the PeproDev Ultimate Invoice plugin to a patched version when available
• Restrict access to the invoice download directory using server-level access controls
• Remove any existing predictably-named ZIP archives from web-accessible directories
• Implement authentication requirements for accessing exported invoice files
• Review access logs for evidence of prior exploitation

Patch Information

Consult the WPScan Vulnerability Advisory for the latest patch information and updated plugin versions. Organizations should update to a version higher than 2.2.5 once a security fix is released by the plugin developer.

Workarounds

• Configure .htaccess rules to deny direct access to the invoice export directory
• Implement server-level authentication for the downloads folder
• Move invoice archives outside the web root and serve through authenticated PHP scripts
• Temporarily disable the bulk download functionality until patched
• Use a security plugin to restrict access to sensitive file types and directories

# Apache .htaccess configuration to restrict ZIP access
# Place in the invoice downloads directory

# Deny all direct access to ZIP files
<FilesMatch "\.zip$">
    Order Allow,Deny
    Deny from all
</FilesMatch>

# Alternative: Require authentication for the entire directory
# AuthType Basic
# AuthName "Restricted Access"
# AuthUserFile /path/to/.htpasswd
# Require valid-user