Initial versions were one-click. The attack became more sophisticated and became zero-click. See https://en.wikipedia.org/wiki/Pegasus_(spyware)#Development_of

Initial versions were one-click. The attack became more sophisticated and became zero-click. See https://en.wikipedia.org/wiki/Pegasus_(spyware)#Development_of_capabilities https://en.wikipedia.org/wiki/Pegasus_(spyware)#Development_... for timeline. See https://en.wikipedia.org/wiki/Pegasus_(spyware)#Saudi_Arabia https://en.wikipedia.org/wiki/Pegasus_(spyware)#Saudi_Arabia for the iMessage version.