Apple has just released iOS 11.0.2 for iPhone, iPad and iPod touch devices. This is the second bug fix update since iOS 11 launched in September. The iOS 11 was on September 19, followed by iOS 11.0.1 a week later.
Apple says the iOS 11.0.2 contains bug fixes, performance improvements, including fix for cracking sounds during audio calls in iPhone 8 and iPhone 8 Plus.
To update, open Settings on your iOS device and go to General → Software Update. You will need at least 50% battery to perform the update, or be connected to a power outlet.