UnderConstructionPage PRO <= 5.76 - Authenticated (Subscriber+) Arbitrary File Read via template_thumbnail Parameter
The UnderConstructionPage PRO plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 5.76. This is due to the plugin accepting arbitrary local file paths in the template_thumbnail parameter and copying their contents into a publicly accessible uploads file. This makes it possible for authenticated attackers, with Subscriber-level access and above, to read arbitrary files on the server, which can contain sensitive information.
Quick answer
Under Construction Page (Pro) should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- *-5.76
Fixed versions
- 5.81
How to fix it
Under Construction Page (Pro) is affected by CVE-2026-11426, a unsafe file upload issue in versions up to 5.76. Wordfence lists the official remediation as updating to version 5.81, or a newer patched version. Prioritize internet-facing WordPress sites, sites with public registration, customer portals, support, booking, import/export, page-builder, and admin workflows where the vulnerable feature is enabled. If immediate patching is not possible, disable the affected plugin or feature, restrict access, and monitor for exploitation until the update is installed.
- Inventory every WordPress site that has Under Construction Page (Pro) installed, including production, staging, multisite, client, WooCommerce, support, booking, and content-management environments.
- Confirm the installed Under Construction Page (Pro) version and compare it with the affected range from the Wordfence advisory.
- Update Under Construction Page (Pro) to version 5.81, or to a newer vendor-supported patched version from the official WordPress update channel.
- If the update cannot be applied immediately, disable Under Construction Page (Pro) or the affected feature and restrict access with roles, authentication, WAF rules, or temporary route blocking.
- Inspect upload directories, plugin storage paths, media folders, backups, snippets, and recently modified files for unexpected scripts, deleted files, webshells, or executable content.
- Rotate administrator sessions, API keys, webhook secrets, payment or integration tokens, and affected credentials if logs or content review suggest compromise.
- Clear WordPress, object, CDN, page-builder, security plugin, WooCommerce, booking/support plugin, and browser caches after patching so vulnerable assets or stored payloads are not served.
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Verify the fix
- Confirm the running Under Construction Page (Pro) version is version 5.81 or newer, and record the patched version in the remediation ticket.
- Verify unsafe file types cannot be uploaded or executed from user-writable paths after the update or mitigation.
- Review web server, WordPress, security plugin, WAF, database, WooCommerce, booking/support, and application logs for exploitation attempts before and after the fix.
- Retest normal visitor, subscriber, customer, editor, administrator, checkout, form, API, booking, support ticket, import/export, backup/restore, snippet, or integration workflows to confirm expected behavior still works.
- Run a fresh Fixnx scan and document the public exposure state, patched version, log review, and any cleanup evidence.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-11426?
Under Construction Page (Pro) versions listed as affected should be reviewed: *-5.76.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.