The big change includes a fix "for an issue where crackling sounds may occur during calls for a small number of iPhone 8 and iPhone 8 Plus devices," according to documentation Apple provided with the software.
While CNBC didn't experience these issues with review units or subsequent devices, some iPhone 8 and iPhone 8 Plus owners have complained about them. The update is available for all iPhones running iOS 11.
The update also fixes a problem where some photos would become hidden and another related to specific attachments to encrypted emails.
The update is available now.