Improper Input Validation
WordPress version 4.9.8 and earlier contains a CWE-20 Input Validation vulnerability in thumbnail processing that can result in remote code execution due to an incomplete fix for CVE-2017-1000600. This attack appears to be exploitable via thumbnail upload by an authenticated user and may require additional plugins in order to be exploited however this has not been confirmed at this time.
CWE-20 - Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.