I never used it, but I would assume yes after reading the frontpage and the doc. At no point there is a PSK set between sender and reciever, not I see any signs for key exchange between devices.
This is not a definitive answer though as I didn’t read the source code of Nfty, nor the UnifiedPush spec.
So use what browsers? Chrome sounds more secure (I didn’t read previous post), yet I don’t want an advertising company looking at my browsing habbits, nor supporting them dominating the browser market share and have a powerful influence on every web standards.