The stagefright exploit can occur when any SMS / MMS app creates the MMS video thumbnail that it shows in the conversation bubble or notification or if a user presses the play button on the video or saves to Gallery.
We have provided a solution for 'StageFright' in Release 3.1 of Textra SMS out now.
Very Important: In other SMS / MMS apps, turning off auto-retrieve is **NOT** enough as once you tap 'download' the exploit potentially becomes active. Additionally you would not get any MMS pics or group messages. Not a good solution.