Some messages sent through WhatsApp can be intercepted and read thanks to a bug in the app, suggests research.
The bug arises because of the way WhatsApp encrypts the messages sent via its service.
Security expert Thomas Boelter found that eavesdropping was possible when circumstances called for encryption keys to be reissued.
Mr Boelter told WhatsApp owner Facebook about the issue in April 2016 but it said it was not working on a fix.
The response he received said that what he had discovered was expected behaviour.