EUVD-2025-16984CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3Description
The HyperComments plugin for WordPress is vulnerable to unauthorized modification of data that can lead to privilege escalation due to a missing capability check on the hc_request_handler function in all versions up to, and including, 1.2.2. This makes it possible for unauthenticated attackers to update arbitrary options on the WordPress site. This can be leveraged to update the default role for registration to administrator and enable user registration for attackers to gain administrative user access to a vulnerable site.
Analysis
The HyperComments WordPress plugin versions up to 1.2.2 contain a critical missing capability check vulnerability in the hc_request_handler function that allows unauthenticated remote attackers to modify arbitrary WordPress options without authentication. This can be directly exploited to escalate privileges by changing the default registration role to administrator and enabling user registration, granting attackers immediate administrative access to vulnerable sites. With a CVSS score of 9.8 and network-based attack vector requiring no user interaction, this vulnerability poses an extreme risk to any unpatched WordPress installation using the affected plugin.
Technical Context
The vulnerability exists in the HyperComments plugin for WordPress, a third-party plugin that extends WordPress comment functionality. The root cause is CWE-862 (Missing Authorization / Capability Check), where the hc_request_handler AJAX action handler fails to verify that the requesting user possesses the required WordPress capability (typically 'manage_options') before processing requests to modify site options. WordPress uses a role-based access control system where 'manage_options' capability is typically restricted to administrators. By exploiting the missing capability check on this publicly-accessible AJAX endpoint, unauthenticated attackers can invoke the handler without authentication and directly call update_option() functions to modify critical WordPress configuration. The attack leverages WordPress's standard option update mechanisms against the plugin's insufficient input validation and authorization controls.
Affected Products
WordPress Plugin: HyperComments, versions <= 1.2.2 (inclusive). Specifically affected versions include 1.0, 1.1, 1.2, and 1.2.2. The vulnerability affects all installations where: (1) the HyperComments plugin is installed and activated, (2) WordPress user registration is enabled or can be enabled (default configuration varies), and (3) the vulnerable hc_request_handler AJAX endpoint is accessible (typical in standard WordPress deployments). CPE data would typically be: cpe:2.3:a:hypercomments:hypercomments:*:*:*:*:*:wordpress:*:* (versions <= 1.2.2). Affected installations span all WordPress deployments (no version restriction on WordPress core) where this plugin is deployed.
Remediation
Immediate remediation steps: (1) Update the HyperComments plugin to version 1.2.3 or later (if available) or the latest stable release from the official WordPress.org plugin repository, as the vendor should have released a patch adding proper capability checks; (2) If no patch is available or delay is expected, immediately deactivate and remove the HyperComments plugin; (3) Review WordPress site options, particularly the default user role (option_name: 'default_role') and user registration settings (option_name: 'users_can_register') for unauthorized modifications; (4) Audit administrator user accounts for unauthorized additions created post-exploitation; (5) Implement WordPress security hardening: enable two-factor authentication for all admin accounts, restrict AJAX endpoints via security plugins, and implement capability-based access controls. Recommended workaround during patch delay: disable user registration on Settings > General and restrict AJAX handler access via .htaccess or firewall rules blocking requests to wp-admin/admin-ajax.php?action=hc_request_handler. Monitor plugin repository for official patch notification and release notes detailing the authorization fix.
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