A Gatelet Custom app whatsapp using Whatsapp.com and Whatsapp.net. is unable to block uploads or inspect content.
CASB Data transfer Gatelet policy example to block all uploads or downloads. A DLP policy that requires content inspection will also fail to inspect the file.
The custom gatelet feature may not correctly detect and inspect a file upload for some applications such as Whatsapp because of the way the SaaS's mechanisms perform the upload including the file ecryption before the upload.
For Whatsapp a Full Gatelet would be required to properly inspect or isolate the file.
A feature request has been created to access the needs and requirements ISFR-2346. A customer can contact support and reference ISFR-2346 to be added or inquire on the status.