Researchers spent six months poking holes in Signal and urge a bigger spotlight on security testing.

Claims of a security hole in WhatsApp’s messenger app were shot down by WhatsApp, which called the allegations false.

Reaction to the release of Google’s Allo messaging app has been mixed since it was unveiled Wednesday during Google’s I/O event. Allo has two modes, a normal mode run by an artificial intelligence that includes Google Assistant. It analyzes messages and offers suggestions based on the content that could include things like restaurant, movie or...