CVE-2024-8016 Overview
CVE-2024-8016 is a PHP Object Injection vulnerability affecting The Events Calendar Pro plugin for WordPress in all versions up to and including 7.0.2. The flaw exists in the deserialization of untrusted input from the filters parameter in plugin widgets. Authenticated attackers with administrator-level access can inject a PHP object, and the presence of a Property-Oriented Programming (POP) chain enables remote code execution. In configurations where the plugin runs alongside Elementor, users with contributor-level access can trigger the issue. The vulnerability is classified under [CWE-502: Deserialization of Untrusted Data].
Critical Impact
Successful exploitation allows authenticated attackers to execute arbitrary PHP code on the WordPress server, leading to full site compromise.
Affected Products
- The Events Calendar Pro for WordPress — all versions up to and including 7.0.2
- WordPress installations running The Events Calendar Pro with Elementor (lower privilege exploitation path)
- Sites using vulnerable widget configurations that expose the filters parameter
Discovery Timeline
- 2024-08-30 - CVE-2024-8016 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-8016
Vulnerability Analysis
The Events Calendar Pro plugin processes user-supplied input from the filters parameter in widget rendering logic. The plugin passes this input to a PHP deserialization routine without validating that the serialized data originates from a trusted source. When PHP unserializes attacker-controlled data, it instantiates arbitrary class objects and triggers their magic methods such as __wakeup() and __destruct().
On its own, object instantiation is not sufficient for code execution. However, WordPress environments typically load many plugins and libraries whose classes can be chained together to form a Property-Oriented Programming (POP) chain. Attackers can leverage these gadgets to reach dangerous sinks such as file writes, SQL execution, or command invocation.
When the site also has Elementor installed, the widget rendering path is reachable by contributor-level accounts, significantly lowering the exploitation barrier from administrator-only to a much broader user population.
Root Cause
The root cause is unsafe use of unserialize() (or equivalent deserialization mechanism) on untrusted request data supplied through the filters widget parameter. The plugin does not enforce type validation, allowlisting of expected classes, or integrity checks before deserialization.
Attack Vector
An authenticated attacker submits a crafted filters parameter value containing a serialized PHP object payload through a request that reaches a vulnerable widget. The plugin deserializes the payload, instantiating attacker-chosen classes. A functional POP chain sourced from installed plugins or themes then drives execution toward arbitrary code invocation on the WordPress host.
The vulnerability manifests through the widget filter deserialization path. Refer to the Wordfence Vulnerability Report and the Events Calendar Pro Security Update for vendor-published technical context.
Detection Methods for CVE-2024-8016
Indicators of Compromise
- Unexpected serialized PHP payloads in HTTP request parameters, particularly values beginning with O: (object) or a: (array) in the filters parameter
- New or modified PHP files in the WordPress wp-content/uploads/ directory or plugin directories with recent timestamps
- Unexpected WordPress administrator accounts, options changes in wp_options, or scheduled tasks in wp_cron
- Outbound network connections from the web server to unfamiliar hosts following widget-related requests
Detection Strategies
- Inspect web server access logs for POST or GET requests to widget-rendering endpoints containing serialized object patterns in the filters parameter
- Deploy web application firewall rules that identify PHP serialization signatures such as O:\d+:" in request bodies
- Monitor PHP error logs for deserialization warnings, missing class errors, or magic method exceptions that indicate probing attempts
Monitoring Recommendations
- Audit contributor and administrator account activity in WordPress, focusing on widget configuration changes
- Track plugin version inventory across managed WordPress sites and alert when The Events Calendar Pro 7.0.2 or earlier remains installed
- Enable file integrity monitoring on WordPress core, plugin, and theme directories to identify unauthorized file writes
How to Mitigate CVE-2024-8016
Immediate Actions Required
- Upgrade The Events Calendar Pro to version 7.0.2.1 or later on all WordPress installations
- Audit user accounts and revoke unnecessary contributor, editor, or administrator privileges
- Review recent widget configuration changes and inspect uploaded files for indicators of compromise
Patch Information
The vendor released version 7.0.2.1 to address the deserialization flaw. See the Events Calendar Pro Release Notes and the Events Calendar Pro Security Update for the official advisory and remediation guidance.
Workarounds
- Temporarily disable The Events Calendar Pro plugin until the patched version can be deployed
- Restrict contributor-level access on sites where Elementor is installed alongside the vulnerable plugin
- Deploy WAF rules that block requests containing PHP serialized object patterns in the filters parameter
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
