Always remember:
"Metadata absolutely tells you everything about somebodyís life. If you have enough metadata, you donít really need content."
NSA General Counsel
Stewart Baker
Check:
"We kill people based on metadata"
https://www.nybooks.com/daily/2014/05/10/we-kill-people-based-metadata/
The problem with open source, while being better than closed source is that there can be discontinuities on the back end that leak. So, for example, the messages my be end to end encrypted and secure when seen from the open sourced code, but asynchronously the server hosts may possess decryption keys.
