Ok, so today was announced that iOS have gap in security. It wouldn't be anything special if not dates - it was there from iOS 7 till now (9.3.5)!
We don't know how long but we know that hackers was using those gaps to instal Pegasus (spyware) just by going to specially prepared sites.
We honestly don't know how many devices are infected but taking into account timeline it's more then "few."
We would still be unaware of danger if not cool mind of Ahmed Mansoor - one of Human Rights Defenders who get link to "secret documents about people tortured by UAE goverment" by SMS. Only his caution prevented him from checking link as fast as posible and he gave it to Citizen Lab where danger was spoted.
Pegasus was created by NSO Group - group of hackers that sells spying software and informations to goverments.
So one more time: Update iOS to newest 9.3.5 version as fast as possible!