CVE-2024-13889: WordPress Importer Plugin RCE Vulnerability

CVE-2024-13889 Overview

CVE-2024-13889 is a PHP Object Injection vulnerability affecting the WordPress Importer plugin in all versions up to and including 0.8.3. The flaw resides in the maybe_unserialize function, which deserializes untrusted input during content import operations. Authenticated attackers with Administrator-level access can inject arbitrary PHP objects into the application. The vulnerability is classified as [CWE-502] Deserialization of Untrusted Data. No Property-Oriented Programming (POP) chain exists in the plugin itself, so exploitation impact depends on other plugins or themes installed on the target site that contain usable POP chains.

Critical Impact
When a POP chain is available from another installed component, attackers can delete arbitrary files, exfiltrate sensitive data, or achieve remote code execution on the WordPress host.

Affected Products

WordPress Importer plugin versions 0.1 through 0.8.3
WordPress sites with the WordPress Importer plugin installed and active
WordPress deployments where additional plugins or themes containing POP chains coexist with the vulnerable importer

Discovery Timeline

2025-03-26 - CVE-2024-13889 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-13889

Vulnerability Analysis

The WordPress Importer plugin processes WXR (WordPress eXtended RSS) files to migrate content between WordPress installations. During this process, the plugin invokes maybe_unserialize on serialized values extracted from post meta, comment meta, and user meta contained in the import file. The maybe_unserialize function calls PHP's native unserialize() when the input matches a serialized data signature. Because the imported XML data is attacker-controlled, an administrator uploading a crafted WXR file triggers deserialization of untrusted objects. The vulnerable deserialization calls appear at multiple locations in class-wp-import.php, including lines 602, 857, 891, and 975.

Root Cause

The root cause is unsafe deserialization of user-supplied content [CWE-502]. The plugin trusts that serialized meta values inside import files originate from a legitimate WordPress export, but the format is easily forged. When unserialize() reconstructs objects, PHP invokes magic methods such as __wakeup and __destruct on the reconstructed classes, allowing execution of arbitrary logic defined by any class loaded in the runtime.

Attack Vector

Exploitation requires Administrator-level authentication on the target WordPress site. The attacker crafts a malicious WXR file containing serialized PHP object payloads embedded in meta fields. When an administrator imports the file through the WordPress Importer interface, the plugin deserializes the payload. The resulting object injection has no immediate impact within the plugin itself. If any installed plugin or theme defines a class with an exploitable magic method chain, that chain can be triggered to delete files, read sensitive data, or execute arbitrary PHP code in the web server context.

The vulnerability was remediated in changeset #3261419, which replaced the unsafe deserialization with safer handling of imported meta values. Full technical details are available in the WordPress Importer source code and the Wordfence advisory.

Detection Methods for CVE-2024-13889

Indicators of Compromise

WXR import files containing serialized PHP object patterns such as O: or C: markers inside <wp:meta_value> elements
Unexpected file creation, deletion, or modification in the WordPress webroot immediately following an import operation
New administrator accounts, scheduled tasks, or PHP files appearing in wp-content/uploads/ after content import
Anomalous outbound network connections from the WordPress host correlated with the import timeframe

Detection Strategies

Inspect WordPress Importer plugin version through the admin plugins page and flag any installation at or below 0.8.3
Monitor wp_import and import_start action executions in WordPress audit logs, correlating them with administrator activity
Scan uploaded WXR files for serialized object signatures before allowing the import to proceed
Review web server logs for POST requests to admin.php?import=wordpress originating from unusual sessions or IP addresses

Monitoring Recommendations

Enable file integrity monitoring on wp-content/plugins/, wp-content/themes/, and wp-content/uploads/ directories
Log all administrator authentication events and correlate them with subsequent import operations
Alert on PHP process spawning shell commands or writing new PHP files during or after an import session
Track outbound DNS and HTTP traffic from the PHP-FPM or Apache worker processes for signs of post-exploitation callbacks

How to Mitigate CVE-2024-13889

Immediate Actions Required

Update the WordPress Importer plugin to a version above 0.8.3 that includes changeset #3261419
Audit installed plugins and themes for classes containing dangerous magic methods that could serve as POP gadgets
Restrict Administrator account access using strong authentication and multi-factor authentication
Remove the WordPress Importer plugin after migration activities are complete rather than leaving it installed

Patch Information

The vendor addressed the issue in changeset #3261419 on the WordPress plugin repository. The patch removes calls to maybe_unserialize on untrusted meta values from imported WXR files. Site administrators should update through the WordPress admin dashboard or via WP-CLI using wp plugin update wordpress-importer.

Workarounds

Deactivate and uninstall the WordPress Importer plugin when it is not actively required for migration tasks
Limit Administrator role assignments to a minimal set of trusted personnel and enforce multi-factor authentication on those accounts
Restrict access to the admin.php?import= endpoints at the web server or WAF layer to specific administrator IP ranges
Validate all WXR files in an isolated staging environment before importing into production

bash

# Update the WordPress Importer plugin via WP-CLI
wp plugin update wordpress-importer

# Verify the installed version is above 0.8.3
wp plugin get wordpress-importer --field=version

# If no longer needed, deactivate and remove the plugin
wp plugin deactivate wordpress-importer
wp plugin uninstall wordpress-importer