Update Your iPhone Right Now
Unlike larger software updates, which might bring some updated features, iOS 14.4.2, iPadOS 14.4.2, and watchOS 7.3.3 are rolling out now to fix an active security exploit that allows malicious websites to potentially engage in universal cross-site scripting. That means if you’re planning to visit any sketchy websites, well, you might be opening yourself up to some problems unless you install the update... More here. Thanks to Kirk.
Don't ignore this update.