https://arstechnica.com/information-technology/2021/09/apple-fixes-imessage-zero-day-exploited-by-pegasus-spyware/

Apple has released several security updates this week to patch a "FORCEDENTRY" vulnerability on iOS devices. The "zero-click, zero-day" vulnerability has been actively exploited by Pegasus, a spyware app developed by the Israeli company NSO Group, which has been known to target activists, journalists, and prominent people around the world.

Tracked as CVE-2021-30860, the vulnerability needs little to no interaction by an iPhone user to be exploited—hence the name "FORCEDENTRY."