Critical XSS Vulnerability in WMF Mobile Redirector//Published on 2026-01-13//CVE-2026-0739

Plugin Name	WMF Mobile Redirector
Type of Vulnerability	Cross-Site Scripting (XSS)
CVE Number	CVE-2026-0739
Urgency	Low
CVE Publish Date	2026-01-13
Source URL	CVE-2026-0739

Executive summary

On 13 January 2026 a stored Cross-Site Scripting (XSS) vulnerability affecting the WordPress plugin “WMF Mobile Redirector” (versions <= 1.2) was publicly disclosed (CVE-2026-0739). The issue permits an authenticated administrator to store JavaScript inside plugin settings fields that is later rendered unsafely, enabling arbitrary script execution in the context of site pages or the admin dashboard when those settings are viewed. Although the attacker must hold an administrator account to store the malicious payload, successful exploitation allows persistent client-side compromise that can be weaponized for persistent redirects, credential theft, backdooring, or other malicious activities.

As WP-Firewall’s security team, we want to walk site owners, developers and incident responders through: what this vulnerability is, who is impacted, practical steps to detect compromise, immediate mitigations (including virtual patching with a WAF), long-term fixes and secure coding practices to prevent similar issues.

Note: If you run WMF Mobile Redirector on any WordPress site, treat this vulnerability as actionable. Even though an attacker needs administrator access to inject the payload, persistent XSS can be leveraged to escalate an attack chain and impact site visitors, editors and administrators.

What is stored XSS and why it matters here

Stored or persistent Cross-Site Scripting occurs when an attacker supplies input that is stored by the application (in a database, options table, or similar) and later rendered into pages without proper output encoding or sanitization. Unlike reflected XSS, stored XSS is persistent — every visitor or admin who views the affected page or interface may run the injected script.

For this vulnerability:

• The attack vector: plugin settings parameters (values stored via the plugin’s settings UI).
• The prerequisite: the attacker must be an authenticated administrator (the plugin’s settings UI requires admin capability).
• The impact: stored JavaScript or HTML may execute in contexts where the stored settings are rendered — potentially both on front-end pages and within wp-admin (depending on plugin behavior).
• The real-world impact: persistent redirections, unauthorized admin actions (CSRF combined with stored XSS), session theft, privacy breach, SEO spam, and persistent client-side backdoors are possible.

Even though the attack requires Admin privileges to plant the payload, we cannot assume an administrator account is always secure. Admin credentials can be leaked, shared, or obtained via other vulnerabilities. Treat stored XSS in admin-editable settings as high-concern for site integrity and reputation.

Vulnerability specifics (high level)

• Affected software: WMF Mobile Redirector plugin for WordPress
• Affected versions: <= 1.2
• Vulnerability class: Authenticated (Administrator+) Stored Cross-Site Scripting (XSS)
• CVE: CVE-2026-0739
• Discovery: reported by a security researcher
• Primary cause: unsafe output of settings parameters without output escaping or sanitization prior to rendering

We do not publish exploit details here. The important technical takeaway for site owners and developers: plugin settings values were not properly sanitized and escaped when saved and/or were printed without required encoding when displayed to users, enabling stored client-side script execution.

Who should be concerned?

• Operators and administrators of WordPress sites that have the WMF Mobile Redirector plugin installed (versions <= 1.2).
• Managed hosters and WordPress maintenance teams who manage multiple sites using this plugin.
• Development teams that maintain custom plugins/themes which interact with mobile redirection or plugin settings stored in options.

Note: Because the ability to inject requires admin privileges, sites where admin accounts are tightly controlled and protected are at lower immediate risk, but compromise of an admin account or misuse by a legitimate admin (malicious insider) still enables exploitation.

Exploitation scenarios and attacker goals

Stored XSS in plugin settings can be abused in multiple ways:

• Persistent defacement or SEO spam: malicious scripts can insert content or hidden links on public pages.
• Credential harvesting: scripts can display fake admin login prompts or exfiltrate cookies/session tokens.
• Session hijacking: capture cookies and send them to an attacker-controlled server.
• Pivot to further compromise: perform admin-in-context actions (submit forms, change settings) on behalf of someone viewing the admin interface if combined with privileged UI access (CSRF-like behavior).
• Distribution of malware: serve external scripts that redirect visitors to malicious payloads or fraudulent sites.
• Persistence for later attacks: inject backdoor scripts that survive plugin/theme updates until cleaned.

Because these scripts are stored and rendered repeatedly, they can be especially damaging to site reputation, SEO, and visitor trust.

Immediate assessment — how to check if you are affected

1. Identify plugin installation and version:
   • From wp-admin: Dashboard → Plugins. Look for “WMF Mobile Redirector” and confirm version.
   • From the file system: inspect the plugin header in the main plugin PHP file.
2. If affected (version <= 1.2), check common storage locations for suspicious HTML/JS:
   • wp_options: plugin settings are commonly stored here.
   • Posts/pages (less likely for settings plugin, but always check).
   • Plugin-specific custom tables if present.

Use these quick checks (WP-CLI recommended):

wp option list --format=csv | grep -i 'wmf\|mobile_redirect\|wmf_mobile'

Search the database for script tags in options and posts:

# Search options for '<script'
wp db query "SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%<script%' LIMIT 50;"
# Search posts and postmeta
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%<script%' LIMIT 50;"
wp db query "SELECT meta_id, meta_key, meta_value FROM wp_postmeta WHERE meta_value LIKE '%<script%' LIMIT 50;"

Grep plugin settings files (if settings are in files):

grep -R --line-number "<script" wp-content/plugins/wmf-mobile-redirector || true

If you find untrusted script tags or suspicious inline JavaScript in stored options or content that you did not place intentionally, treat it as compromise and follow the incident response steps below.

Indicators of compromise (IoCs)

• Unexpected redirects from your site to unknown domains.
• Hidden or injected iframes, script tags, or on-event attributes in pages or admin screens.
• Unauthorized changes to plugin settings that you didn’t make.
• New admin users or login events from unknown IPs around the time of changes.
• Outbound HTTP requests from the browser to unknown third-party domains when viewing site pages.
• Alerts from external scanners detecting JavaScript-based SEO spam.

Check server and application logs for unusual POST requests to plugin settings pages or options saving endpoints (e.g., admin-post.php, options.php, or plugin-specific admin pages). Also examine the timing of admin actions in the WordPress audit logs (if available).

Immediate containment & mitigation steps

If you discover suspicious stored scripts or believe you’re affected, act quickly:

1. Temporarily restrict access
   • Immediately restrict admin dashboard access to a small set of IP addresses if possible (via host firewall, server ACLs, or plugin-based IP restrictions).
   • Rotate administrator passwords and invalidate active sessions for all users:
     • In wp-admin: Users → All Users → Edit each Admin → Change password
     • Or use WP-CLI to force logout by altering authentication tokens:

       wp user session destroy <user_id>

   • Revoke or rotate API keys and credentials used by the site.
2. Take the site to maintenance mode (if necessary)
   • Prevent visitors from being served malicious scripts while you investigate.
   • Use server-level redirects or the WordPress maintenance plugins.
3. Clean stored payloads
   • Remove suspicious script tags from wp_options, posts, postmeta or plugin tables. Prefer manual review to avoid deleting legitimate data.
   • Example SQL to view and then remove tags (test first, and backup DB first):

     SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%<script%' LIMIT 100;
     -- To remove script tags safely you may use application logic; direct SQL replace is risky.
     

   • Use a trusted security plugin or WP-CLI to search-and-remove suspicious content, but ensure you have backups.
4. Disable the vulnerable plugin
   • If an update/fix is not available, deactivate and remove the plugin until a secure version is released.
   • Command:

     wp plugin deactivate wmf-mobile-redirector

5. Scan & audit
   • Run a full site scan for malware and additional injected content.
   • Check themes, mu-plugins, and uploads directories for unexpected files.
   • Review user accounts and capabilities for unauthorized additions.
6. Restore from a known-good backup (if available)
   • If you have clean backups from before the compromise and the timeline of the malicious change is clear, restoring may be the safest route. Ensure credentials and any vulnerable plugins are patched before bringing the restored site online.

Detection rules (WAF / monitoring) — examples you can apply now

While awaiting vendor patching, virtual patching with a WAF (Web Application Firewall) can reduce risk by blocking attempts to store XSS payloads. As WP-Firewall security operators, here are practical rule ideas you can deploy immediately.

Important: Do not block legitimate administration traffic indiscriminately. Use a combination of blocking, logging, and challenge responses (CAPTCHA) where possible.

1. Block inbound admin requests containing scriptish payloads in plugin settings endpoints:
   • Rule concept: If an HTTP POST to any request path that includes wmf-mobile-redirector or common options-saving endpoints (/wp-admin/options.php, /wp-admin/admin-post.php) contains <script, javascript:, onerror=, onload=, or suspicious event-handler attributes, then block or challenge the request.
   • Example (pseudo-regex for match & logging — tune to minimize false positives):
     • Detect payload patterns: (<script\b|javascript:|onerror\s*=|onload\s*=|<img\s+[^>]*onerror=|<svg\b[^>]*onload=)
   • Action: block or return 403 for the POST; log details and notify site admin.
2. Enforce input validation / stripping on admin-side saves:
   • If possible, filter request body to remove <script> tags and inline event attributes before allowing a save to proceed.
   • Replace or strip: <script>, <iframe>, on\w+=, javascript: in admin POST bodies for plugin settings routes.
3. Rate-limit or require 2FA on admin users:
   • Apply increased protection to admin accounts: require multi-factor, limit login attempts, and challenge suspicious admin requests.
4. Monitor for suspicious content being rendered:
   • Detect when pages or admin screens include <script> or eval( in stored option output unexpectedly and flag an alert.
5. Protect search & replace and DB import endpoints:
   • Block mass admin operations that might be used to inject content.

Note: These WAF patterns should be deployed with monitoring first to observe false positives. Avoid breaking legitimate admin flows. A staged approach (log-only → challenge → block) is recommended.

Recommended investigative commands and queries

Always back up your database before modifying it. Examples below are for triage and cleanup.

• Export all options that contain angle-bracket data:

  wp db query "SELECT option_name, LEFT(option_value, 1000) as preview FROM wp_options WHERE option_value RLIKE '<[^>]+'& LIMIT 200;" --skip-column-names
  

• Dump suspicious option values for offline review:

  wp db query "SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%<script%' LIMIT 200;" > suspicious_options.sql
  

• Temporarily snapshot current plugin directory for offline analysis:

  tar -czf /root/wmf-mobile-redirector-snapshot-$(date +%F).tgz wp-content/plugins/wmf-mobile-redirector
  

• Check for modified admin files or unknown files:

  find wp-content -type f -mtime -30 -ls
  

Mitigation and remediation — recommended steps

1. If an official plugin update is released: apply it immediately.
   • Update the plugin from wp-admin or WP-CLI:

     wp plugin update wmf-mobile-redirector

2. If no official fix is available:
   • Remove or deactivate the plugin until a patched release is provided.
   • Consider replacing the plugin with a well-maintained alternative or implement required functionality in a secure, maintained custom solution.
3. Clean stored payloads thoroughly:
   • Manually review and remove suspicious content from wp_options and other DB tables.
   • When cleaning, check both the visible front-end effects and admin screens to ensure no remnants remain.
4. Rotate credentials and sessions:
   • Change admin passwords, revoke API keys, and invalidate sessions.
   • Reissue any tokens and inform any users with admin privileges to update their credentials.
5. Conduct a full security audit:
   • Scan for additional malware, backdoors, and unauthorized admin users.
   • Check server logs for footholds or lateral movement.
6. Harden admin access:
   • Enforce strong passwords and multi-factor authentication for admins.
   • Use role separation: create lower-privileged editorial roles where possible; avoid shared admin accounts.
7. Improve monitoring:
   • Implement file integrity monitoring, change detection on sensitive DB keys, and admin action logging.
8. Restore and validate:
   • If you restore from backup, validate that the vulnerability is closed and all admin credentials are reset before opening the site to users.

Secure development guidance for plugin authors (how this should have been prevented)

If you’re a plugin or theme developer, follow these secure coding practices:

• Validate and sanitize input on save:
  • Use appropriate sanitization functions (e.g., sanitize_text_field(), wp_kses() with a safe allowed list for HTML, or custom sanitizer for expected input).
  • Never assume admin input is safe; administrators can be compromised.
• Escape output at rendering time:
  • Use esc_html() for plain text, esc_attr() for attributes, wp_kses_post() when outputting limited HTML, or wp_kses() with a strictly defined allowed list.
  • Prefer escaping at output instead of only sanitizing at input — defense in depth.
• Check capabilities and nonces:
  • Verify current_user_can() for the required capability before saving settings.
  • Enforce check_admin_referer() or nonce verification to prevent CSRF-assisted attacks.
• Avoid storing raw HTML unnecessarily:
  • If you expect plain text in a setting, store and render it as plain text.
• Use prepared statements and safe database APIs:
  • When interacting with the database directly, use $wpdb->prepare() and WordPress APIs to avoid other injection classes.
• Unit and security tests:
  • Add tests that attempt to store and render script-like inputs and assert that output is escaped.

Incident response playbook (concise)

1. Triage: Confirm plugin version and presence of suspicious stored scripts.
2. Contain: Remove plugin from production or block admin access to a limited IP range; enable maintenance mode.
3. Eradicate: Remove malicious scripts from DB; delete or replace compromised files.
4. Recover: Restore from clean backup (if available) after updates and credential rotation; harden the site.
5. Lessons learned: Record timeline, root cause, and improvements (patch management, monitoring, role hardening).

Long-term protections and best practices

• Keep plugins/themes/core updated and subscribe to security notices for software you run.
• Limit the number of administrator accounts; apply principle of least privilege.
• Use multi-factor authentication for all admin users.
• Enable logging of admin actions and set up alerts for suspicious activity (new plugin activations, settings changes).
• Deploy a Web Application Firewall (WAF) that supports virtual patching to block known exploit patterns until an official patch is available.
• Schedule regular site scans (malware and integrity checks) and DB inspections for injected scripts or malicious links.
• Enforce code review for all plugins/themes before deployment.

How WP-Firewall protects you (brief overview)

As a WordPress firewall/security service provider, our approach focuses on layered controls to reduce exposure to vulnerabilities like stored XSS:

• Managed WAF rules and virtual patching that can be deployed immediately to block attempts to save or render dangerous payloads.
• Managed scanning and automated detection for stored XSS signatures in options, posts and plugin-specific storage.
• Automated alerts and recommended remediation guidance to help you remove malicious content quickly.
• Hardening and access control recommendations to reduce the chance of an administrator account being compromised in the first place.

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Features of the Basic (Free) plan:

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• WAF (Web Application Firewall) rules and virtual patching for known risks
• Malware scanner to detect stored XSS and other injected scripts
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Final notes and responsible disclosure

• CVE-2026-0739 has been assigned to this issue. If you manage affected sites, treat this as actionable and prioritize triage and mitigation.
• If you discover stored XSS on your site and need help investigating or cleaning your WordPress instance, WP-Firewall provides incident support and managed remediation services.
• If you are a plugin developer, adopt the secure development guidelines above and consider security-focused code review prior to releasing updates.

For questions about deploying WAF rules, virtual patching, or assistance with investigation and cleanup, our WP-Firewall Support team is available to help.

— WP-Firewall Security Team