On my HTC One M7, using a freshly installed Firefox with no modifications, the CPU usage hovers around 40% consistently. And goes to 80% when changing pages. I have researched this and found tips on how to resolve, my question is, why in heck d0 I have to modify a stock install to keep my phone from overheating and draining the battery? The usage remains after pressing the Android home button which is supposed to idle the thing for the most part. It is my opinion that an app available on the Play Store should already be optimized for battery consumption, cpu usage, and thermal performance and not to make your phone feel like you're playing a graphics intensive game. Not even watching HD you tube videos causes so much heat. I un installed Firefox and installed Opera and have had no issues with excessive battery consumption, excessive cpu usage, or excessive heat. Albeit a little laggy, but at least my leg isn't getting cooked. I can't imagine my hardware is to blame, should be easily duplicate able on any Android 5 device. I will try other devices I have at home none the less.