Apple has released an emergency update for iPhones, iPads and Macs amid fears of a dangerous bug.
The updates are numbered 15.4.1 for the iPhone and iPad, and 12.3.1 for the Mac.
They bring some small changes, including a fix for a battery bug that meant that iPhones and iPads lost charge more quickly than they should after a recent update. While it is not clear how widespread that bug was, affected users said their devices had been losing charge more quickly since iOS 15.4 was released.
iOS 15.4 was made available by Apple in mid-March, and included a range of features, including the ability to unlock an iPhone while wearing a mask.
But as well as that battery fix, the new updates also fix a critical security bug that Apple warned could already have been used by hackers.
It did not give detailed information about those bugs, how exactly they could be exploited or how many people are likely to have been hacked. The company often withholds informations about such security flaws so that attackers are not able to exploit them.
Installing the latest updates should however secure devices against anyone trying to make use of the attack.
That is done by opening up the Settings app, clicking through to software updates, and pressing the option to install the new version of the operating system. Macs, iPhones and iPads should also prompt users to update too.
Apple has pushed out a number of security updates over the year, aimed at fixing similarly dangerous bugs.