Apple took the very unusual move of releasing a second iOS 11.4 beta this week. The fifth version of the developer beta came out on Monday, and its replacement debuted today.

This could mean good things for the imminent release of this iPhone and iPad operating system update, or it could be a bad sign.

Earlier this week, news of the EFAIL security problem broke. This exploit gives an attacker access the contents of encrypted messages. An iOS update is required to protect Apple’s mobile devices from it. It’s quite possible the fix has just been added to iOS 11.4 beta 6.

A less cheery possibility is that Apple might have hurried out beta 6 because beta 5 introduced some severe bug that needed to be fixed without delay. However, there’ve been no reports of such a problem.

What’s definitely in iOS 11.4 beta 6

One of the biggest additions to iOS 11.4 is backing up Messages on iCloud. Just like your calendar and contacts data, this upcoming feature stores copies of your texts so you can retrieve them if something happens to your phone.  

There’s also the long-awaited addition of AirPlay 2, allowing a single source to send audio to multiple speakers, including HomePods. 

Both of these were originally going to be part of iOS 11.3 but were dropped during the beta process.

Anyone who wants to participate in the Apple Beta Software Program can sign up today. It’s free to all who are willing to take the risk of using software on their iPhone and iPad that’s known to contain bugs.

The launch date for the the non-beta version of iOS 11.4 remains unknown. Obviously, Apple’s been beta testing it for weeks now, so a full release is expected soon.