MacRumors published a story that Apple has released iOS 15.4.1.

Apple Releases iOS 15.4.1 With Fix for Battery Drain Issue

Apple today released iOS 15.4.1 and iPadOS 15.4.1, minor updates to the iOS and iPadOS 15 operating systems that were released in September. iOS 15.4.1 and iPadOS 15.4.1 come two weeks after the launch of iOS 15.4.

The iOS 15.4.1 and iPadOS 15.4.1 updates can be downloaded for free and the software is available on all eligible devices over-the-air in the Settings app. To access the new software, go to Settings > General > Software Update.

  Apple Releases iOS 15.4.1 With Fix for Battery Drain Issue