affiliate-toolkit <= 3.9.2 - Authenticated (Contributor+) Arbitrary File Upload via 'atkp_product_largeimageurl' Parameter

The affiliate-toolkit – Multi-Network Affiliate & Amazon Product Display plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 3.9.2 via the upload_image function. This is due to insufficient file type validation in upload_image due to a weak Content-Type prefix check and extension derivation from the attacker-controlled URL path, with no dangerous-extension stripping. This makes it possible for authenticated attackers, with contributor-level access and above, to upload files that may be executable, which makes remote code execution possible. Exploitation requires the "import product image" option to be enabled in the plugin settings, as this activates the image download pipeline triggered on product post save.