WordPress Marketplace additional-preview-images.php Arbitrary File Upload

There exists an arbitrary file upload vulnerability in all versions of WordPress Marketplace (currently removed from the WordPress.org plugin directory). The vulnerability exists due to the wpmp_upload_previews() method making no attempt to validate input. The vulnerability publicly serves up the upload directory and executes PHP that is requested. The plugin is currently unsupported.

Exploitation

Stages

1. An attacker sends an upload request to a vulnerable WordPress instance containing an arbitrary file.
   
   
2. The server responds with a ‘200’ response code and the name of the uploaded file with ‘wpdm-adp-‘ appended to the beginning of the file name concatenated with a time stamp. The name of the uploaded file follows.
   
   
3. The attacker requests the uploaded file from the directory ‘/wp-content/uploads/wpmp-previews/’. PHP will then be executed.

Prerequisites

The attack is unauthenticated and needs to be posted to an endpoint with ‘task=wpmp_upload_previews’.

Alert Logic Coverage

Alert Logic® has evaluated its customer base for exposure to the exploit and has developed signatures for mitigating the threat depending on the security service in place.

The Network-Based Intrusion Detection System (IDS) has been updated with the new signatures for this exploit when detected via Alert Logic Threat Manager™. If this signature is detected, an incident is generated in the Alert Logic console.

Recommendations for Mitigation

Upgrade to a non-vulnerable version to mitigate this vulnerability.