The Image Optimizer, Resizer and CDN – Sirv plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the sirv_upload_file_by_chanks AJAX action in all versions up to, and including, 7.2.6. This makes it possible for authenticated attackers, with Contributor-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.
https://plugins.trac.wordpress.org/changeset/3103410/sirv/trunk/sirv.php