The firmware came out with the number iOS 14.4.2 and, according to the company, all users must urgently install it. The fact is that the update closes a serious vulnerability in the Webkit engine for the Safari browser. Due to this error, attackers can gain access to user data. It doesn’t matter if you are using Safari or another third-party browser.
The update weighs about 200 MB and has already begun to be distributed over the air to all supported devices.
By the way, besides iOS 14.4.2, Apple also released iPadOS 14.4.2 with a similar fix.