WhatsApp, with more than 1.2 billion active users, is one of the easiest ways to send secure information. “With WhatsApp, it’s as simple as sending a text message — but it’s encrypted,” Mr. Dance explained. I'm not a security expert but I think this is not exactly the best practice. This may have been true pre-fb acquisition but there has been changes to how WhatsApp behaves, especially server side storage. Also the…
myth_buster, lisper, & newscracker make interesting points. In researching WhatsApp a while ago, I came across this in a Quora post "But one more point I want to stress here is that, though whatsapp is allowing end to end communication , it does not necessarily mean they can not analyse the encrypted data. in cryptography we call it Searchable Encryption." ( https://www.quora.com/Now-that-WhatsApp-can-no-longer-read-…
It not being open source is a political argument, not a technical one.
EDIT: I ended up doing just that. It took roughly 5 minutes (most of that was making sure I had my PATH for Java set up correctly on this machine) to get decompiled Java code ready to inspect.