CVE-2026-13422 Overview
CVE-2026-13422 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the HD Quiz plugin for WordPress in versions 2.2.0 through 2.2.1. The flaw stems from missing or incorrect nonce validation in the hdq_validate_nonce function. Unauthenticated attackers can delete or modify quizzes and questions, create new quizzes, and change plugin settings through forged requests. Exploitation requires tricking a site administrator into performing an action such as clicking a malicious link. The vulnerability is categorized under [CWE-352] and has an EPSS probability of 0.179%.
Critical Impact
Unauthenticated attackers can modify or delete quiz content and change plugin settings by tricking authenticated administrators into visiting a crafted page.
Affected Products
- HD Quiz plugin for WordPress version 2.2.0
- HD Quiz plugin for WordPress version 2.2.1
- WordPress sites running HD Quiz in the affected version range
Discovery Timeline
- 2026-06-27 - CVE-2026-13422 published to NVD
- 2026-06-29 - Last updated in NVD database
Technical Details for CVE-2026-13422
Vulnerability Analysis
The HD Quiz plugin exposes several AJAX actions that handle quiz creation, modification, deletion, and settings updates. These handlers rely on the hdq_validate_nonce function defined in includes/functions.php to verify request authenticity. In versions 2.2.0 and 2.2.1 this function is implemented incorrectly, so nonce checks either do not occur or do not fail on invalid input. As a result, WordPress cannot distinguish between legitimate administrator requests and forged requests originating from external origins.
An attacker hosts a page that issues requests to endpoints registered in includes/actions-ajax.php. When an administrator with an active WordPress session visits the page, the browser attaches session cookies to the outgoing request. The vulnerable handler processes the request as if the administrator initiated it. This allows attackers to abuse privileged AJAX actions without holding credentials themselves.
Root Cause
The root cause is broken CSRF protection in the hdq_validate_nonce helper referenced by multiple AJAX action handlers, including those at lines 7, 53, 68, 87, 155, and 179 of actions-ajax.php. Correct WordPress practice requires calling check_ajax_referer or wp_verify_nonce with a valid nonce action, then rejecting the request when verification fails. The vulnerable versions do not enforce this control on state-changing operations.
Attack Vector
Exploitation occurs over the network and requires user interaction from a privileged WordPress user. The attacker crafts an HTML page or email that triggers a POST or GET request to the vulnerable admin-ajax.php endpoint. When an authenticated administrator loads the attacker-controlled content, the browser submits the request with valid session cookies. The plugin then executes the requested quiz modification, deletion, or settings change on behalf of the victim. No confidentiality impact occurs, but integrity of quiz data and plugin configuration is affected.
For technical review of the affected code paths, see the Wordfence Vulnerability Analysis and the HD Quiz functions.php source.
Detection Methods for CVE-2026-13422
Indicators of Compromise
- Unexpected creation, modification, or deletion of quizzes and quiz questions in the WordPress database tables used by HD Quiz.
- Changes to HD Quiz plugin settings that no administrator recalls making.
- POST requests to wp-admin/admin-ajax.php targeting HD Quiz action parameters from external referrers.
- Administrator browser sessions loading unfamiliar third-party pages shortly before configuration changes.
Detection Strategies
- Review web server access logs for admin-ajax.php requests carrying HD Quiz actions with Referer headers pointing outside the site's own domain.
- Compare current plugin settings and quiz records against known-good backups to identify unauthorized modifications.
- Audit the WordPress wp_options table and quiz-related custom tables for timestamps that do not correlate with legitimate admin activity.
Monitoring Recommendations
- Enable a WordPress activity logging plugin to record administrator actions and plugin setting changes.
- Alert on HTTP requests to HD Quiz AJAX endpoints that lack a same-origin Referer or contain no valid _wpnonce parameter.
- Monitor for phishing emails or messages sent to administrators containing links to unfamiliar domains.
How to Mitigate CVE-2026-13422
Immediate Actions Required
- Upgrade the HD Quiz plugin to version 2.2.2 or later, which corrects the nonce validation logic in includes/functions.php.
- Force logout of all administrator sessions and require password resets if unauthorized quiz or settings changes are observed.
- Restore quiz content and plugin settings from a clean backup if tampering is confirmed.
Patch Information
The vendor released a fix in HD Quiz version 2.2.2. The updated hdq_validate_nonce implementation is visible at the HD Quiz 2.2.2 functions.php reference. Update through the WordPress plugin dashboard or by replacing the plugin files manually.
Workarounds
- Deactivate the HD Quiz plugin until the site can be updated to version 2.2.2.
- Restrict access to wp-admin using IP allowlists at the web server or WAF layer to reduce exposure to forged requests.
- Train administrators to avoid clicking untrusted links while logged into WordPress and to use a separate browser profile for administrative work.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
