Formidable (aka node-formidable) 2.1.0 through 3.x before 3.5.3 relies on hexoid to prevent guessing of filenames for untrusted executable content; however, hexoid is documented as not "cryptographically secure." (Also, there is a scenario in which only the last two characters of a hexoid string need to be guessed, but this is not often relevant.) NOTE: this does not imply that, in a typical use case, attackers will be able to exploit any hexoid behavior to upload and execute their own content.
An arbitrary file upload vulnerability in formidable v3.1.4 allows attackers to execute arbitrary code via a crafted filename. NOTE: some third parties dispute this issue because the product has common use cases in which uploading arbitrary files is the desired behavior. Also, there are configuration options in all versions that can change the default behavior of how files are handled. Strapi does not consider this to be a valid vulnerability.