Apple today released an updated version of iOS 17.6.1, with the new software coming a week and a half after the launch of the original iOS 17.6.1 update. The new version has a build number of 21G101, up from 21G93.
iOS 17.6.1 can be downloaded on eligible iPhones and iPads over-the-air by going to Settings > General > Software Update.
According to Apple's release notes, the iOS 17.6.1 update addresses an issue that could prevent the enabling or disabling of Advanced Data Protection. It is not clear what is different between the new version of the software and the original version.
The Advanced Data Protection bug impacted a small number of users. Those who tried to turn Advanced Data Protection on and weren't able to get it enabled saw an error message and it was clear it wasn't active. Affected users who tried to turn it off saw it disabled in the interface, though it was actually still active for iCloud data.
Both of those bugs have been fixed in the update. iPhone users who had the bug that prevented Advanced Data Protection from properly turning off will see a notification that asks them to confirm the decision to turn the feature off after installing iOS 17.6.1. Apple says that the few users who experienced this bug had an expected level of security or more, in the situation where ADP did not turn off as expected.
Source: Macrumors