CVE-2026-11363 Overview
The Ninja Forms – The Contact Form Builder That Grows With You plugin for WordPress contains a PHP Object Injection vulnerability affecting all versions up to and including 3.14.6. The flaw stems from deserialization of untrusted input during form import operations [CWE-502]. Authenticated attackers with administrator-level access can inject arbitrary PHP objects into the application. The vulnerability requires a Property-Oriented Programming (POP) chain from another installed plugin or theme to achieve impact such as arbitrary file deletion, sensitive data disclosure, or code execution.
Critical Impact
Administrator-level attackers can inject PHP objects that, when combined with a POP chain from another installed component, may enable arbitrary file deletion, sensitive data exfiltration, or remote code execution on the WordPress host.
Affected Products
- Ninja Forms – The Contact Form Builder That Grows With You (WordPress plugin)
- All versions up to and including 3.14.6
- WordPress sites with additional plugins or themes containing a usable POP chain
Discovery Timeline
- 2026-09-09 - CVE-2026-11363 published to the National Vulnerability Database (NVD)
- 2026-09-09 - Last updated in NVD database
Technical Details for CVE-2026-11363
Vulnerability Analysis
The vulnerability resides in the plugin's form import workflow. When an administrator imports a crafted form, the WPN_Helper::build_nf_cache() function invokes $action->get_settings() immediately after import. This code path triggers PHP deserialization of attacker-controlled data through the plugin's Model implementation in includes/Abstracts/Model.php.
Because the deserialization occurs automatically during the import action, no additional user interaction is required beyond submitting the crafted form file. The Ninja Forms codebase itself does not ship a viable POP chain, so exploitation depends on gadgets present in other plugins or themes installed on the target site. When such gadgets exist, attackers can chain them to perform arbitrary file operations, disclose sensitive data, or execute arbitrary code within the WordPress process.
Root Cause
The root cause is unsafe use of PHP's unserialize() on data sourced from an imported form file without integrity validation or safe deserialization controls. The import handler in includes/Admin/Processes/ImportForm.php accepts serialized settings that flow into Model.php at line 344, where deserialization occurs. This maps to [CWE-502: Deserialization of Untrusted Data].
Attack Vector
The attack requires an authenticated administrator session. The attacker prepares a Ninja Forms export file containing a serialized PHP object graph designed to trigger a POP chain in another installed component. The administrator imports the file through the plugin's Import/Export menu (includes/Admin/Menus/ImportExport.php). The import processor deserializes the payload, instantiating the crafted objects and executing the chain's side effects. Attackers may deliver the malicious file through social engineering, a compromised lower-privileged account escalating via a second flaw, or supply chain compromise of a form template repository.
The vulnerability is described in prose only; consult the Wordfence Vulnerability Report and the Ninja Forms Changeset Reference for verified technical detail.
Detection Methods for CVE-2026-11363
Indicators of Compromise
- Unexpected Ninja Forms import events in WordPress audit logs, particularly outside of normal administrator activity windows
- Presence of serialized PHP object markers (for example, O:, a:, or class names) inside imported .nff form files
- New or modified PHP files, cron entries, or WordPress options created immediately following a form import
- Outbound network connections from the web server process shortly after an import action
Detection Strategies
- Inspect uploaded form import files for serialized object structures referencing classes from other installed plugins or themes
- Monitor invocations of WPN_Helper::build_nf_cache() and ImportForm.php handlers through PHP application logging or web server access logs
- Correlate administrator authentication events with subsequent import requests to identify anomalous sequences
- Alert on modifications to wp-content/plugins/ or wp-content/themes/ directories following a form import
Monitoring Recommendations
- Enable WordPress activity logging that captures plugin import and export operations with the acting user and source IP
- Ingest web server, PHP-FPM, and WordPress audit logs into a centralized analytics pipeline for correlation with file integrity events
- Baseline normal administrator behavior and alert on rare or first-time import actions from any account
- Track file integrity across the WordPress installation, focusing on wp-content directories writable by the web server
How to Mitigate CVE-2026-11363
Immediate Actions Required
- Upgrade the Ninja Forms plugin to a version above 3.14.6 that includes the fix referenced in the plugin changeset
- Audit installed plugins and themes for known POP chain gadgets and remove any that are unused or unmaintained
- Restrict WordPress administrator accounts, enforce multi-factor authentication, and rotate credentials for any suspect accounts
- Review recent Ninja Forms import activity and investigate any imports performed by unexpected users or at unusual times
Patch Information
The vendor addressed the deserialization flow in a patched release tracked by the Ninja Forms Changeset Reference. Site administrators should update through the WordPress plugin manager or by deploying the patched package directly. Review the Ninja Forms Model Implementation and Ninja Forms Import Form Process to confirm the fixed code paths after upgrade.
Workarounds
- Temporarily disable the Ninja Forms Import/Export menu for all administrators until the plugin is upgraded
- Restrict administrator access to trusted network ranges using web server access controls or a web application firewall rule
- Remove or disable plugins and themes not required for production operation to reduce the pool of exploitable POP chain gadgets
- Apply a virtual patch at the WAF layer that blocks form import requests containing serialized PHP object markers such as O: followed by a class name
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
