The GPX Viewer plugin for WordPress is vulnerable to arbitrary file creation due to a missing capability check and file type validation in the gpxv_file_upload() function in all versions up to, and including, 2.2.9. This makes it possible for authenticated attackers, with subscriber-level access and above, to create arbitrary files on the affected site's server which may make remote code execution possible.
https://plugins.trac.wordpress.org/browser/gpx-viewer/tags/2.2.9/gpx-viewer-admin.php#L144