It's known that this information was shared by a fairly reputable account on X (formerly Twitter), who shared build number 21B91 for today's update.

Last week, Macrumors first reported that Apple was internally testing iOS 17.1.1, based on evidence of software versions in their analysis logs on their website. The update is likely to focus on bug fixes and security patches.
Unfortunately, it's unclear which bugs Apple will address in iOS 17.1.1. It may include similar bug fixes for Wi-Fi connectivity issues that Apple deployed in the iOS 17.2 beta, while also addressing issues where some iPhone models shut down overnight. Apple also promises to fix the wireless charging issue with BMW affecting the lineup in an unspecified update later this year.
iOS 17.2 is still in the beta testing phase and is expected to be released in December. This update brings quite a few changes and new features such as the Diary app, the ability for Apple Music subscribers to collaborate on playlists, the Translate option for the Action button on models, and the security option for Contact Verification in iMessage.
Read more: iOS 17.2 will launch later this year with these 10 new features