It's addressed the eavesdropping flaw, but not all features are working.

Apple pushed out an iPhone update earlier this month to fix a Group FaceTime security problem, which let people eavesdrop on each other, but apparently hasn't gotten all the bugs out yet.

People on the MacRumors forum noticed that two people on a FaceTime call can't add a third person, with the button to add someone grayed out, as previously reported.

We're glad to help with adding a person to Group FaceTime. It's good that you've updated to iOS 12.1.4. Check to be sure that the person you're adding has also updated. Let us know what happens.

— Apple Support (@AppleSupport) February 15, 2019

Apple Support confirmed this limitation on Twitter, after noting that you have to update to iOS 12.1.4 to use Group FaceTime at all. The feature was temporarily disabled after a Fortnite-playing teen discovered the bug.

So, for now, Group FaceTime might not work for some users for a number of reasons. First, all users on a Group FaceTime call need to be on iOS 12.1.4. Secondly, the 'Add Person' feature is not working the way explained in a Group FaceTime support document Apple published at the time it released iOS 12.1.4.

Apple now released a beta 3 update for the latest Group FaceTime bug, but unlike the patch for the eavesdropping attack, it might not be rushed out and may be bundled with iOS 12.2, which is currently in beta. 

Source: cnet