Whatsapp partners with Cloudflare to verify that Whatsapp Web hasn't been tampered with

Whatsapp chooses Cloudflare to ensure that its javascript code for Whatsapp Web isn't tampered with when it's downloaded on the client browser.

This serves as an additional guarantee to users of Whatsapp, that the code used to enable the Whatsapp communications hasn't been tampered with. 

This could happen at the source, on Whatsapp's end, if they were ever to be compromised. Or it could happen while the code is being downloaded from a malicious website, because the user device has been compromised.

To ensure that tampered Whastapp Web code isn't downloaded and executed on the client browser, Cloudflare will store the hash files on its own systems and make them available for verification when Whatsapp Web is installed or updated on a target system.

The Cloudflare annoucement