The Customizer Export/Import plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the '_import' function in all versions up to, and including, 0.9.7. This makes it possible for authenticated attackers, with Administrator-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible. NOTE: This vulnerability is only exploitable when used in conjunction with a race condition as the uploaded file is deleted shortly after it is created.
https://plugins.trac.wordpress.org/changeset/3144365/customizer-export-import