Plugin Name	Video Onclick
Type of Vulnerability	Cross-Site Scripting (XSS)
CVE Number	CVE-2026-1608
Urgency	Medium
CVE Publish Date	2026-02-08
Source URL	CVE-2026-1608

CVE-2026-1608 — Stored XSS Vulnerability in Video Onclick Plugin (≤ 0.4.7): Essential Insights for WordPress Site Owners and Developers

An authenticated contributor-level stored Cross-Site Scripting (XSS) vulnerability exists in the Video Onclick WordPress plugin (versions up to 0.4.7), caused by insufficient sanitization of shortcode input. This advisory covers the nature of the risk, how attackers exploit it, detection strategies, immediate mitigations, and recommended long-term developer best practices.

Executive Summary

• Vulnerability Type: Authenticated stored Cross-Site Scripting (XSS) via shortcode misuse (CVE-2026-1608).
• Affected Versions: Video Onclick versions ≤ 0.4.7
• Required Access Level: Contributor role or higher
• Potential Impact: Stored XSS allows attackers to inject malicious JavaScript that executes in the browsers of privileged users viewing affected pages. CVSS score 6.5 (medium severity) with scope for escalation depending on context.
• Immediate Recommended Actions: Deactivate or uninstall the plugin; if removal isn’t possible, disable shortcode rendering immediately; scan and cleanse posts/comments containing dangerous shortcodes; review and tighten user privileges; rotate administrative credentials; implement additional access controls.
• Developer Guidance: Enforce rigorous sanitization and escaping of all shortcode inputs using WordPress core functions such as esc_attr(), esc_url(), and wp_kses() to prevent injection.

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Understanding the Risk: Stored XSS via WordPress Shortcodes

Shortcodes are a convenient method for plugin authors to embed dynamic content, like video players or interactive elements, within posts and pages. However, they accept user-supplied attributes and content, which, when improperly sanitized, can become vectors for code injection.

The Video Onclick plugin’s vulnerability allows an authenticated contributor to insert malicious JavaScript payloads through shortcode attributes or content that get stored in the database and rendered whenever privileged users access affected pages. The result is a classic stored XSS attack, presenting a significant risk as it targets trusted users without requiring them to visit external, malicious sites.

While exploit requires contributor-level access, many WordPress sites provide such permissions to external users, contractors, or content submitters, which increases attack surface due to potential account misuse.

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Real-World Impact and Exploit Paths

This stored XSS vulnerability can be exploited in several concerning ways:

• Administrator and Editor Session Hijacking: When high-privilege users view the injected shortcode, injected JavaScript can steal cookies, hijack sessions, make privileged AJAX calls, or perform actions like installing backdoors and modifying site options.
• Content Review Manipulation: Editors previewing content with the malicious shortcode risk running the payload, resulting in compromised accounts.
• Site Visitor Attacks: If the shortcode renders on the front-end for general visitors, malvertising, redirects, or cryptominer injection may occur.
• Complex Exploits: Despite browser defenses like Content Security Policy (CSP) and HttpOnly cookies, attackers may leverage XSS to conduct more sophisticated CSRF or social engineering attacks with elevated privileges.

Remember, stored XSS persists in the database and remains after the attacker account is removed, requiring careful detection and cleanup.

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Technical Overview of the Vulnerability

The vulnerability stems from the plugin outputting shortcode attributes and content directly into HTML without sufficient sanitization or escaping.

Vulnerable example (simplified PHP pseudo-code):

function video_onclick_shortcode($atts, $content = '') {
    $a = shortcode_atts(array(
        'src' => '',
        'title' => ''
    ), $atts);

    // Unsafe: Output without escaping attributes and content
    $html = '<div class="video-onclick" data-src="' . $a['src'] . '" title="' . $a['title'] . '">';
    $html .= $content;
    $html .= '</div>';

    return $html;
}
add_shortcode('video_onclick', 'video_onclick_shortcode');

Issues include:

• Attributes are directly concatenated into HTML without esc_attr() or esc_url().
• Content is rendered raw without wp_kses() filtering.
• URLs and other inputs lack validation.
• Attackers can inject event handlers or script tags by breaking out of HTML attribute contexts.

Safer implementation example:

function video_onclick_shortcode($atts, $content = '') {
    $a = shortcode_atts(array(
        'src' => '',
        'title' => ''
    ), $atts);

    $src = esc_url_raw($a['src']);
    $title = esc_attr(sanitize_text_field($a['title']));
    $content = wp_kses_post($content);

    $html = '<div class="video-onclick" data-src="' . esc_attr($src) . '" title="' . $title . '">';
    $html .= $content;
    $html .= '</div>';

    return $html;
}

Key takeaway: Always validate and sanitize inputs and escape output thoroughly.

---

Proof-of-Concept Summary (Conceptual)

• An attacker with Contributor privileges submits a shortcode with malicious payloads, e.g.:
  • [video_onclick src="..."]<script>/* malicious code */</script>[/video_onclick]
  • Or: [video_onclick title='x" onmouseover="/* payload */']
• Privileged users viewing affected content unwittingly execute the JavaScript payload.

Mitigating risk includes restricting how contributor content is reviewed and hardening privilege models.

---

Immediate Response Actions for WordPress Site Owners

1. Deactivate or Remove the Plugin
   Immediately disable the Video Onclick plugin if it is not critical.
2. Disable Shortcode Rendering if Removal Isn’t Feasible
   Implement this MU plugin or insert into your theme’s functions.php to deactivate the shortcode:

   <?php
   add_action('init', function() {
       if (shortcode_exists('video_onclick')) {
           remove_shortcode('video_onclick');
       }
   }, 20);
   

3. Scan for Infected Content
   Use WP-CLI or SQL queries to locate posts containing the shortcode:

   WP-CLI example:

   wp post list --post_type='post,page' --format=ids | xargs -n1 -I % wp post get % --field=post_content | grep -n "\[video_onclick"

   SQL example:

   SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%[video_onclick%';

4. Clean or Remove Malicious Content
   Edit posts to strip injected scripts or unsafe shortcode content. Use wp_kses_post() or other filtering as appropriate.
5. Audit Contributor and Higher Privileged Accounts
   Remove or suspend suspect accounts. Enforce strong passwords and two-factor authentication (2FA).
6. Rotate Administrator Credentials and Sessions
   Change admin passwords and log out active sessions if compromise is suspected.
7. Run Full Site Malware Scans and Integrity Checks
   Verify there are no backdoors or persistent threats.
8. Apply Virtual Patching via Web Application Firewall (WAF)
   Deploy rules to block suspicious shortcode payloads or script tags in requests (see the example WAF rules below).

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Example Temporary WAF Rules (Conceptual)

1. Block POST requests containing the video_onclick shortcode concatenated with script or event attributes:
   • Pattern: (\[video_onclick[^\]]*(<script|javascript:|onerror=|onmouseover=|onclick=))
   • Action: Block or CAPTCHA challenge.
2. Block script tags submitted to post editing endpoints:
   • Pattern: <script[^>]*>
   • Scope: POST requests to /wp-admin/post.php, /wp-admin/post-new.php, xmlrpc.php, and admin-ajax.php.
3. Monitor or block JavaScript event handler attributes:
   • Pattern: (on\w+\s*=|javascript:)
   • Action: Alert with optional blocking after thorough testing.

Note: Test all rules in staging environments to prevent disruption to legitimate use cases.

---

Detecting Exploitation: A Checklist

• Review post content for the video_onclick shortcode with embedded <script> tags or suspicious attributes.
• Investigate user accounts with Contributor and above roles, focusing on new or suspicious accounts.
• Analyze recent admin activities or plugin installs around timeline of suspicious content.
• Inspect web server access logs for unusual POST requests containing shortcode or script payloads.
• Monitor browser consoles during content preview as an editor/admin for unexpected script execution.
• Check filesystem integrity and recent file modifications that could hint at backdoors.
• Examine scheduled WordPress cron jobs for unfamiliar tasks.

---

Incident Response Protocol

1. Take site offline or restrict admin access temporarily.
2. Back up entire site and database for investigation.
3. Remove vulnerable plugin and any malicious content.
4. Rotate all privileged user credentials and invalidate sessions.
5. Conduct thorough malware and integrity scans; restore from pre-compromise backups as necessary.
6. Audit logs to reconstruct attack timeline and origin.
7. Engage security professionals if managed service is available.
8. Return to live operation only after confirming threat neutralization.

---

Long-Term Security Hardening for Site Administrators

• Enforce the principle of least privilege; only grant necessary capabilities.
• Implement content moderation workflows requiring review before privileged users access content.
• Mandate strong authentication methods including 2FA for all admins and editors.
• Keep all plugins and themes up-to-date and sourced from trusted origins.
• Restrict shortcode usage based on user roles where feasible.
• Deploy Content Security Policy (CSP) headers as an additional defense layer.
• Monitor content changes, new user creation, and unusual activity continuously.
• Use automated scanning tools regularly to detect XSS and vulnerability regressions.

---

Developer Best Practices: Securing Shortcodes Against XSS

Plugin developers must adhere to strict input handling patterns:

1. Treat all shortcode input as untrusted and sanitize rigorously:
   • Use shortcode_atts() to normalize user attributes.
   • Validate URL attributes with esc_url_raw() and confirm allowed protocols.
   • Sanitize text attributes with sanitize_text_field() and escape output with esc_attr().
   • Sanitize content with wp_kses() limiting allowed HTML tags.
2. Escape all output immediately before rendering, never trust pre-escaped input.
3. Avoid building HTML with raw string concatenations of untrusted data.
4. Secure all AJAX/admin endpoints with appropriate capability checks and nonce verification.
5. Develop unit and integration tests that simulate malicious input and ensure it is sanitized.
6. Implement logging for interactions that include suspicious shortcode usage or JavaScript injections.

Example of a secure shortcode callback function:

function secure_video_onclick_shortcode($atts, $content = '') {
    $a = shortcode_atts(array(
        'src'   => '',
        'title' => '',
    ), $atts, 'video_onclick');

    $src = esc_url_raw($a['src']);
    $title = sanitize_text_field($a['title']);

    $allowed_tags = array(
        'p' => array(),
        'br' => array(),
        'strong' => array(),
        'em' => array(),
    );
    $content = wp_kses($content, $allowed_tags);

    $html = '<div class="video-onclick" data-src="' . esc_attr($src) . '" title="' . esc_attr($title) . '">';
    $html .= $content;
    $html .= '</div>';

    return $html;
}
add_shortcode('video_onclick', 'secure_video_onclick_shortcode');

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How Managed-WP Supports Your Security Needs

As a leading WordPress managed security provider, Managed-WP offers comprehensive protections and expert support to minimize your exposure and respond rapidly when vulnerabilities surface:

• Managed custom firewall rules: Blocking known exploitation patterns like malicious shortcodes, script tags, or dangerous event attributes without changing your plugin code.
• Malware scanning and detection: Automated scans identify shell scripts, injected payloads, and compromised content.
• Virtual patching for immediate protection: When vendor patches are delayed, Managed-WP deploys WAF-level rules to protect your site without waiting.
• Incident support and cleanup guidance: Step-by-step remediation assistance, plus active cleanup services on paid plans.

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Cleanup Queries and Automation Scripts

Identify posts containing suspicious shortcodes and <script> tags:

SELECT ID, post_title, post_type, post_status
FROM wp_posts
WHERE post_content LIKE '%[video_onclick%'
AND post_content LIKE '%<script%';

Example PHP snippet to remove script tags from affected posts (backup your database before running):

<?php
$posts = get_posts(array(
    's' => '[video_onclick',
    'posts_per_page' => -1,
    'post_type' => array('post','page'),
));

foreach ($posts as $post) {
    $clean_content = preg_replace('#<script(.*?)>(.*?)</script>#is', '', $post->post_content);
    if ($clean_content !== $post->post_content) {
        wp_update_post(array(
            'ID' => $post->ID,
            'post_content' => $clean_content,
        ));
    }
}

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Verifying Remediation and Testing Security

• Confirm no rendering of video_onclick shortcodes on the front-end after disabling/removal.
• Use a contributor test account to submit shortcodes containing harmless test payloads (e.g., </div><img src=x onerror='console.log("test")'>) and verify they are sanitized or removed.
• Inspect browser developer tools to ensure no unexpected inline scripts execute.
• Monitor Managed-WP firewall logs for blocked malicious attempts and fine-tune rules accordingly.

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Recommendations for Plugin Reviewers and Maintainers

• Thoroughly audit shortcode use and user-supplied attributes/content for injection vectors.
• Restrict shortcode availability in admin-only previews without strict sanitization.
• Clearly document accepted attributes and sanitize inputs accordingly.
• Consider providing site owners options to disable shortcodes globally or conditionally.
• Respond quickly to vulnerability reports with patched releases and recommend virtual patch signatures to WAF providers.

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Practical Security Checklist

• Deactivate and remove unused or unsupported plugins immediately.
• Disable the video_onclick shortcode if you cannot upgrade the plugin.
• Search for and cleanse posts containing shortcode-based scripts.
• Audit and moderate contributor and higher permissions rigorously.
• Enforce WAF blocking rules for suspicious shortcode payloads.
• Rotate admin credentials and enforce multifactor authentication.
• Run regular malware and integrity scans.
• Continuously follow hardening best practices including CSP and least privilege.

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