The TheGem theme for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the thegem_get_logo_url() function in all versions up to, and including, 5.10.3. This makes it possible for authenticated attackers, with Subscriber-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.
https://themeforest.net/item/thegem-creative-multipurpose-highperformance-wordpress-theme/16061685