Apple confirmed to fix the overheating issue of iPhone 15 series iPhones by software update. Apple also confirmed the issue is due to a software bug. According to Apple, the titanium frame used in the iPhone 15 Pro series is not causing any heating issue.

Earlier iPhone 15 users reported overheating issues, which is now acknowledged by Apple. The overheating issue is due to a bug in iOS 17.  According to Apple, the overheating issue is not affecting the long-term performance of the iPhone 15  devices. Apple will be fixing iPhone 15 overheating issues in the future iOS updates. 
The heating issue is due software related and   third-party apps like Instagram, Uber, and Asphalt 9 seems to be a contributing factor. Apple is working on the fixes with these developers.

Apple introduced a titanium frame to the iPhone 15 Pro and iPhone 15 Pro Max models, which makes this device distinguishable from the non-pro model. Apple also replaced the ring/silent switch with the new Action Button in the iPhone 15 Pro and iPhone 15 Pro models. This feature is exciting for the iPhone Pro model lovers.
People are saying that the use of titanium frame in iPhone 15 Pro and iPhone 15 Pro Max models is causing the heating issue. According to Apple, the titanium frame  is not responsible for the heating issues. Apple will release a software update to fix the heating problem.

Earlier Apple analyst Ming-Chi Kuo speculated that the use of titanium frame might prohibit heat disbursal difficulty resulting in overheating in the iPhone 15 Pro and iPhone 15 Pro Max models. Overheating is a big issue being faced by the users of iPhone 15 devices. Apple confirmed to fix the overheating issue by software update.
Apple will be fixing overheating issues in the iOS 17.1 update. Currently this update is being tested by Apple as part of beta testing. This update is expected to be released later this month.

According to Apple, the heating issue is also due to third-party apps. Apple is working with the developers of these applications to fix the issue in their application. Applications such as Instagram, Uber, and Asphalt 9 are believed to be causing heating issues.

This good news is that the overheating issue is not going to impact long-term performance of the iPhone 15 services. Apple confirmed that there won’t be an issue on the long-term use of these phones due to overheating problems. The users of iPhone 15 series are waiting for the next update of iOS 17 to get the fix for the overheating issue.