Apple today released iOS 26.6 and iPadOS 26.6, updates to the iOS and iPadOS 26 operating systems that came out in September. iOS 26.6 comes a month after the launch of iOS 26.5.2, a security update. iOS 26.6 and iPadOS 26.6 can be downloaded on eligible iPhones and iPads over-the-air by going to Settings > General > Software Update. According to Apple's release notes, iOS 26.6 and iPadOS 26.6 include security fixes for the iPhone and iPad.
This notice is for 26.6, you may be thinking of 27 (which the September releases are always a bit of a hassle, yeah.)