iOS 8.4 Serios Crash!

I updated my iPhone and iPad on iOS 8.4 and i install an app from appstore called "betternet". When i open that app on my iPhone then my iPhone turned restarted like my screen burnt and damaged and got stuck in very serios bootloop. After this i open this app on iPad my iPad got crashed same as on my iPhone. by some way i turn off my bootloop stucked iPhone and after restart then i press home button then again it crashes because

Betternet app is opened after crash. Then i turned off again bootloop stucked iphone and and turn on and then delete app without opening multitasking. Now iphone ipad working well. Otherwise it may can seriously damaged iOS devices. I heard many news and read some review of people on app in appstore of crashing. Apple should fix it because it looks too much serious.