CVE-2026-39473: Simple History Information Disclosure Flaw

CVE-2026-39473 Overview

CVE-2026-39473 is an Insertion of Sensitive Information Into Sent Data vulnerability affecting the Simple History plugin for WordPress, developed by Pär Thernström. This vulnerability allows attackers to retrieve embedded sensitive data from the plugin's output, potentially exposing confidential information that should not be accessible to unauthorized users.

The Simple History plugin is a popular WordPress activity logging tool that tracks user actions and site changes. Due to improper handling of sensitive information, the plugin may inadvertently expose confidential data in its responses, creating a significant privacy and security risk for WordPress site administrators and their users.

Critical Impact

Sensitive information exposure can lead to unauthorized access to confidential data, potential account compromise, and privacy violations affecting WordPress site users and administrators.

Affected Products

• Simple History WordPress Plugin versions through 5.24.0
• WordPress installations with Simple History plugin enabled
• Sites using Simple History for activity logging and audit trails

Discovery Timeline

• 2026-04-08 - CVE CVE-2026-39473 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-39473

Vulnerability Analysis

This vulnerability is classified as CWE-201 (Insertion of Sensitive Information Into Sent Data). The Simple History plugin fails to properly sanitize or filter sensitive information before including it in data sent to users. This can result in the exposure of sensitive data that should be restricted, such as user credentials, API keys, internal system details, or other confidential information logged by the plugin.

The vulnerability affects all versions of the Simple History plugin from initial release through version 5.24.0. WordPress sites using this plugin for activity logging may inadvertently expose sensitive data to users who should not have access to such information.

Root Cause

The root cause of this vulnerability lies in the plugin's failure to implement proper data sanitization and access controls when retrieving and displaying logged information. The Simple History plugin logs various user activities and system events, but does not adequately filter sensitive information before presenting it in the user interface or API responses.

This type of vulnerability typically occurs when:

• Logging mechanisms capture more data than necessary
• Output functions do not properly redact sensitive fields
• Access controls fail to restrict data visibility based on user privileges

Attack Vector

An attacker can exploit this vulnerability by accessing the Simple History plugin's data retrieval functionality. The attack does not require authentication in some scenarios, depending on how the plugin is configured. By querying the plugin's logs or data export features, an attacker can retrieve embedded sensitive data that was inadvertently stored or transmitted.

The exploitation process involves:

1. Identifying a WordPress site with the vulnerable Simple History plugin installed
2. Accessing the plugin's log viewing or data export functionality
3. Extracting sensitive information from the returned data
4. Using the exposed data for further attacks or unauthorized access

For detailed technical information about this vulnerability, refer to the Patchstack Vulnerability Report.

Detection Methods for CVE-2026-39473

Indicators of Compromise

• Unusual access patterns to Simple History plugin endpoints or admin pages
• Unexpected data export requests from the Simple History plugin
• Anomalous queries targeting activity log data
• Evidence of unauthorized access to WordPress admin areas related to Simple History

Detection Strategies

• Monitor WordPress access logs for suspicious requests to Simple History plugin endpoints
• Implement file integrity monitoring on WordPress plugin directories
• Review Simple History plugin access logs for unauthorized data retrieval attempts
• Configure web application firewalls to detect unusual data extraction patterns

Monitoring Recommendations

• Enable detailed logging for all Simple History plugin access and data exports
• Set up alerts for bulk data retrieval from the Simple History logs
• Monitor for new or unauthorized WordPress admin users who access logging features
• Regularly audit Simple History plugin permissions and access controls

How to Mitigate CVE-2026-39473

Immediate Actions Required

• Update the Simple History plugin to the latest patched version immediately
• Review Simple History logs for evidence of unauthorized data access
• Audit WordPress user permissions related to Simple History plugin access
• Consider temporarily disabling the plugin if an update is not available

Patch Information

WordPress site administrators should update the Simple History plugin to a version newer than 5.24.0 that addresses this vulnerability. Check the Patchstack Vulnerability Report for the latest patch information and recommended update procedures.

To update the plugin:

1. Navigate to WordPress Admin → Plugins
2. Locate Simple History in the plugin list
3. Click "Update Now" if an update is available
4. Verify the updated version number is greater than 5.24.0

Workarounds

• Restrict access to the Simple History plugin to only trusted administrators
• Implement additional WordPress security plugins to limit access to sensitive features
• Configure web application firewall rules to block suspicious requests targeting the plugin
• Consider disabling public-facing Simple History features until patched
• Review and sanitize existing log data to remove any exposed sensitive information

# WordPress CLI command to update Simple History plugin
wp plugin update simple-history

# Verify current plugin version
wp plugin list --name=simple-history --fields=name,version,status

# Temporarily deactivate plugin if needed
wp plugin deactivate simple-history