Apple released a significant security update for iPhones and iPads on Friday to patch newly discovered security vulnerabilities in the devices’ system software.

The issue was discovered by researchers at the University of Toronto’s Citizen Lab, who said the software flaw was being “actively exploited” to deliver commercial spyware called Pegasus developed and sold by the Israeli company NSO Group.

Pegasus is an expensive tool typically used to target dissidents, journalists and political opponents, so ordinary users likely have little to fear. Still, Citizen Lab recommended that all users should “immediately” update their devices.

The software can install itself on a phone without requiring users to click a link, and gives the hacker complete access to the entire contents of the phone, as well as the ability to use its cameras and microphone undetected.

In recent years, NSO Group has found itself embroiled in international scandal after being accused of providing the highly invasive spyware to countries with poor human rights records who used it to spy on dissidents, journalists and activists — including Azerbaijan, Bahrain, Kazakhstan, Morocco, Rwanda, Saudi Arabia, Hungary, India and the UAE.

NSO Group has repeatedly denied claims that its spyware has been used to target human rights activists, and says that it only sells to government entities with the approval of the Israeli government, as a tool for catching criminals and terrorists. The company is the subject of ongoing probes and investigations in many countries around the world.

How to install the update:

To install the update, users should open Settings on their iPhone, then select “General” followed by “Software Update.”

Tap to begin installation of the iOS 16.6.1.

If the update is not there, go back to the General page, then tap “About” to check the iOS version number.

If it’s 16.6.1, the phone or tablet already has the update installed.

If the phone is still using 16.6 or an earlier version, repeat the above steps.

If there still isn’t an update, try restarting the phone.

If that doesn’t make the update appear, double-check the internet connection and then wait a bit before trying again.