Default Thumbnail Plus <= 1.0.2.3 - Authenticated (Contributor+) Arbitrary File Upload

Description

The Default Thumbnail Plus plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the 'get_cache_image' function in all versions up to, and including, 1.0.2.3. This makes it possible for authenticated attackers, with contributor-level and above permissions, to upload arbitrary files on the affected site's server which may make remote code execution possible.