CVE-2026-1655: WordPress EventPrime Auth Bypass Flaw

CVE-2026-1655 Overview

The EventPrime plugin for WordPress contains a Missing Authorization vulnerability (CWE-862) that allows authenticated attackers with minimal privileges (Customer role and above) to modify event posts created by administrators. The flaw exists in the save_frontend_event_submission function, which accepts a user-controlled event_id parameter and updates the corresponding event post without enforcing proper ownership or capability checks.

Critical Impact

Authenticated attackers can manipulate administrator-created event posts by exploiting missing authorization checks in the event submission handler, potentially leading to content tampering or misinformation on affected WordPress sites.

Affected Products

• EventPrime Event Calendar Management plugin for WordPress versions up to and including 4.2.8.4
• WordPress sites utilizing the EventPrime plugin with frontend event submission functionality
• Any site where authenticated users (Customer+ role) have access to event submission features

Discovery Timeline

• 2026-02-18 - CVE-2026-1655 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-1655

Vulnerability Analysis

This vulnerability represents a classic broken access control flaw where the application fails to verify that the authenticated user has proper authorization to modify a specific resource. The save_frontend_event_submission function processes event updates without implementing ownership validation or capability checks, creating an Insecure Direct Object Reference (IDOR) condition.

The attack requires authenticated access at the Customer privilege level or higher, plus the ability to obtain a valid WordPress nonce. While the nonce requirement provides some protection against cross-site request forgery, it does not prevent authenticated users from directly exploiting the vulnerability. The impact is limited to integrity compromise (unauthorized modification of posts) without affecting confidentiality or availability.

Root Cause

The root cause is the absence of authorization checks in the save_frontend_event_submission function located in class-ep-ajax.php. The function accepts the event_id parameter from user input and proceeds to update the event post without verifying:

1. Whether the current user owns the event they're attempting to modify
2. Whether the current user has the edit_posts or equivalent capability for the target post
3. Whether the event belongs to the user's allowed scope of modifications

This design oversight allows any authenticated user who can access the submission endpoint to manipulate events belonging to other users, including administrators.

Attack Vector

The attack vector is network-based and requires the following conditions:

1. Authentication: The attacker must be authenticated to the WordPress site with at least Customer-level privileges
2. Nonce Acquisition: A valid nonce must be obtained (typically available to authenticated users via legitimate site interaction)
3. Event ID Discovery: The attacker needs to know or enumerate valid event IDs (often predictable sequential integers)

The vulnerability is exploited by submitting a request to the AJAX handler with a manipulated event_id parameter pointing to an event created by an administrator or another user. The function processes the update request without ownership validation, allowing the attacker to modify event details, potentially including event titles, descriptions, dates, and other metadata.

Technical details of the vulnerable code can be found in the EventPrime source code at line 741 and line 798.

Detection Methods for CVE-2026-1655

Indicators of Compromise

• Unexpected modifications to event posts, particularly changes to events created by administrators
• Audit log entries showing event updates by users who did not create those events
• AJAX requests to save_frontend_event_submission containing event_id values not owned by the requesting user
• Suspicious patterns of event enumeration attempts followed by modification requests

Detection Strategies

• Monitor WordPress AJAX handlers for save_frontend_event_submission actions with mismatched user ownership
• Implement logging for all event modification requests, capturing the requesting user ID and target event author
• Deploy web application firewall rules to detect parameter manipulation patterns targeting event IDs
• Review access logs for sequential event_id enumeration patterns from authenticated users

Monitoring Recommendations

• Enable WordPress audit logging plugins to track all post modifications with user attribution
• Configure alerts for event modifications by users who are not the original authors
• Monitor for unusual volumes of AJAX requests to EventPrime endpoints from single user accounts
• Implement real-time integrity monitoring for high-visibility or critical event posts

How to Mitigate CVE-2026-1655

Immediate Actions Required

• Update the EventPrime plugin to the latest patched version immediately
• Review recent event modifications to identify any unauthorized changes made before patching
• Temporarily restrict frontend event submission functionality if immediate update is not possible
• Audit user accounts for suspicious activity patterns related to event management

Patch Information

The EventPrime development team has released a security patch addressing this vulnerability. The fix implements proper authorization checks to verify that users can only modify events they have created or have explicit capabilities to edit. Review the official changeset for technical details of the fix. Additional analysis is available in the Wordfence Vulnerability Report.

Workarounds

• Disable frontend event submission functionality temporarily by removing user capabilities for event creation
• Implement a WordPress capability plugin to restrict event editing to administrators only
• Add custom authorization hooks to the EventPrime submission handler to validate ownership before processing
• Use a Web Application Firewall (WAF) rule to block AJAX requests with suspicious event_id manipulation patterns

# Temporarily disable EventPrime frontend submissions via wp-config.php
# Add to wp-config.php before "That's all, stop editing!" line
define('EP_DISABLE_FRONTEND_SUBMISSION', true);